Jeremy,
My 2cents, worth all you've paid.
Adapters work some times and then other times do not. It's the same in the Windows world as it is in the Mac world. SCSI, USB, FW, it all depends very much upon a level of magic that can some times even vary depending upon versions of mother boards. I've used many different cards and adapters over the years and once I get something that works I try to not change ANYTHING. Avoid them, avoid them, avoid them. Or if you need to be very careful about making changes, something very hard to do these days with automatic OS updates.
MacBook, MBP, iMac, MacMini, MAB, so many choices, all of them good. A LOT of deciding which computer is best is dependent upon what you are doing with it, and where. I changed from a MacMini to a new PowerBook for the fact that I want to compute in bed, at the table, when I travel. I did not get a very powerful system as I do not do any processing with what I shot at the present time. While I know I have enough to power to work I know I will need to add more memory (max it out when ever you can). I wanted a robust body so I did not need to worry, so I actually got a slower processor. My wife and my kids have a firewire on their two macs so we are covered there.
From what you say I read what you really need is a KICK A55 desktop. While a laptop would be fun, what you want to do is serious image crunching stuff. For that I would look into which has the faster graphics processing chip set (memory is a big part here) between the Mini and the iMac. My gut says the iMac will win. Another part of the picture is the ease of adding a second monitor. I say this because I would use one monitor for the image and another for controls, browsers windows and all. I've love the Mac from the Mac II days because it's so easy to add second monitors. With the mini you can get an adapter to fake it out, but I think the nod goes to the iMac. I remember when I looked for a Mac for a group I was supporting about a year ago the iMac rocked for their graphics needs.
Perhaps the larger iMac would not need a second monitor it has a lot of room on that screen. I'd get a track-ball and perhaps look for a continuous feed ink system printer.
Now about buying a notebook for taking with you to show and basic work (not high end image processing, say word processing) I would hold off for a few months. Apple just released the beta version of the iTouch/iPhone OS 3.0. It looks very interesting if they were to come out with say a somewhat larger pad. Say the size you see the crew of the NCC-1701-D walking around with. I just have a feeling that Apple might do to the NetBook what they did to the MP-3 players a few years back. There are already a lot of applications out there and even more on the way. It might be this summer some time, just in time for the incoming class for next years college students. While the price will be higher than the other NetBooks (my guess is around $550 USD) the application prices and volume will slam the door shut on another market. Now this is not based upon any inside information, just a guess. Somewhat tea leave reading based upon a few years inside and lots of years watching. I'd be happy with a larger screen for showing my shots on and in a perfect world an attachment to a VGA output to attach to a projector.
Beware, your mileage will vary.
B2 (;->