Hey Samouraï - why do you prefer to be on Linux - philosophical reasons or other? I ask, as a Linux (amongst other things) user because I think that this answer will help to get you the most helpful advice.
In my case I'm using Linux for philosophical reasons - partly because I resent Adobe's move to subscription model where you (well I) never own the software - I don't care if Lightroom (LR) is cheaper this way, I don't want to keep paying for it forever, according to their rules. Alternatively I won't use pirated or somehow circumvented copies because I don't want to pursue my hobby with someone else's stolen intellectual property. So given that I'm also not using older copies of LR or PS because updates for new cameras is a hassle, etc... And I don't want to live in the past!
But, all this means that I live with a series of compromises. The Linux software all has it's own unique learning curves, arguably it isn't as good as commercial software (but can be better aswell) but that often has nothing to do with inherent quality of the software and more to do with understanding the UNIX headset - i.e. lots of small programs that do exactly one thing really well. The right specific tool for the job rather than an all 1001 uses tool. But more recent Linux programs seem to be going this way.
Some considerations for you -
1: Do you want a colour profiled display? There are plenty of options:
https://en.wikipedia.org/wiki/Linux_color_management But it will take research and time and fiddling. I haven't done this yet.
2. Non-destructive workflow. Photivo isn't a one stop solution. Photivo recommends itself as a developer, not a manager and not “Gimp” (so no layers and massive number of plugins presumably). As the site says Photivo is intended to be used in a workflow together with digiKam/F-Spot/Shotwell (all managers) and Gimp.
3: Organisation: I use Shotwell. It imports all of my raw and legacy and Tiff (scans) files transparently. It organises okay and handles the 12,000 + 110MB of image files that I've currently managed to get into one single archive. When you're in Shotwell you can always revert to the original, untouched file. But it's not a powerful versioning solution and it isn't perfect - sometimes not finding images (that are there) and it crashes on occasion. But I've used it to organise a Pictures directory by Year-Month-Day and I can use any program to interrogate that. I think I can get all of my originals and move them elsewhere anytime, unaltered. But it's not '1 click' cradle to grave solution like LR. Shotwell allows you to set both an external photo editor and external RAW editor (accessed via right clicking on the image). So I'm set up to open jpegs (and TIFFs) in Gimp and Raw files in Darktable. Overall it's stable enough and simple / basic enough to work well at collecting all my files reliably.
4: Post Processing. I've moved towards Darktable recently (as in during the last week!) - it's 16bit, handles Tiff files (Rawtherapee doesn't). But it takes mucho RAM so make sure if you use Darktable that you have a 64bit Linux distro and use the 64bit version of Darktable. Ask me how I know this? Darktable is non-destructive and you can set Shotwell to use it as the default RAW editor (or whatever you choose to use). Darktable seems stable.
5: GIMP. For heavy hitting photo editing I don't see how you can get around not using GIMP as a photoshop equivalent. There are always going to be compromised images that we don't bin, but which need layers and so on to fix or salvage. But GIMP is 8bit. Now some people will tell you this is S&*%T! and go on an expletive filled rampage (but rarely if ever with image examples to back up the assertions made). I don't know, lots of people seem happy with it aswell. I do know that 8 bit's is half the data of 16 bits and if I import a 30 MB tiff into GIMP and over-write that file in Gimp ... hey presto circa 15 MB file. There are some alternatives perhaps Krita is a 16 bit drawing program, its from the KDE side of Linux - it might serve ... I haven't used it though. There are lots of workarounds discussed online about GIMP's 8 bit limitations. You would need to explore just how big (or possibly not) a problem this is.
6: Wine. I also have a legacy camera (SIGMA DP1) and I run its Windows software on Wine as a native application. No problems, I use wine to run an older version of SIGMA's Photo Pro program for X3f files without hassle and export to jpeg or print directly from there - all works fine for me at what Wine calls "Gold" standard. I mention Wine because apparently PhotoShop CS4 also runs as a gold standard application. This might solve some potential GIMP is 8 bit problems. I can open X3f files from inside Linux and it will open the relevant Wine application seamlessly and I can save from that WINE application to the Linux filesystem.
7: Virtualbox. I run my scanner in a Virtual Machine using Vuescan. No problems, never crashes, no speed hassles. Runs perfectly. I only use windows XP, but you could run Windows 7 for much broader support of more recent applications. But XP does me for my scanner and I scan directly to the Linux Pictures directory. I mention Virtual box and WINE because they might help you plug a gap or task that Linux can't natively handle.
8: Tethering. Does Phase One do tethering? If that's a reason to use then Darktable (apparently) offers tethering. Currently it's the only solution that does in Linux.
9: Distro. I run Ubuntu (14.04 LTS) with the Gnome 3 alternative interface. It has some of the OSX features I like (i.e. expose) and a dock of sorts. Plus I like the simple folder and icon layout that reminds me of my OS/2 days (ah, the OS/2 warp Dock and an object oriented interface!) I also use a Surface Pro 3 which I really like and is a great lightweight touchscreen device that I can do real work on, but not my hobby (well not this one anyway). Like you, I used to really like OSX but I feel that Apple have gone from offering the consumer a road to travel on to telling the consumer that theirs' is the only road to travel on and no you won't stop at the little independent coffee shop along the side of the road. No the only coffee you can drink on this road is our blend, from our shop. Garr!
10. Ease of updating. I recommend a Debian based system like Ubuntu. Once you learn that you can update / upgrade with a terminal command like "Sudo apt-get install WHATEVERPROGRAM" and the system takes care of all the wrinkles and hassles. It's a slick system.
Programs I haven't considered - Rawtherapee, UFRAW (standalone but also used by other programs to handle RAW import) and a million other solutions that exist out there and are more or less actively being developed or not. Lightzone comes to mind - it used to be commercial but is now open source. Runs on Windows and OSX as well as Linux. Another lightroom alternative. I'm not sure how important a 10bit GPU is photography. I don't play games on my photography computer, ymmv.
As you can see, it's a long piece of string!
