Dave,
I recently bought an used M8 that came with several batteries and an assortment of accessories. There have been a couple extra costs that I hadn't fully thought out. First was getting all the UV/IR filters for my lenses. 50 Summicron, 35 Summicron, and 21 SA which took a while to locate a 48mm filter for it. After some time using it I found the batteries that came with it were showing their age so I ordered two new batteries. I would anticipate buying two batteries right away after buying the camera. It is a real disappointment to be out working and have your batteries go dead.
Looking at how you show your work I think that Adobe Lightroom would be more than sufficient for your editing needs. Considering that you could still move a file from LR to PS for additional editing. One thing to keep in my with this is if you buy a new Apple computer running OS 10.7 your current version of PS will not be compatible forcing you to upgrade to CS5.
The iMac suggested earlier would also be my recommendation for the perfect balance of cost and performance. I do find myself doing most my editing on my Macbook Pro 15" over my MacPro tower due to the fact it allows me to edit whenever I have free time which is normally during my lunch break at work.
As for a Summilux lens. I wish I had one but tend to feel that I can get by with out that extra stop. I find that I use the 35mm lens far more often on the M8 due to the sensor crop since it is far closer to a 50mm on my film bodies. I now find myself considering a 28mm lens to give me the 35mm equivalent. This has been my most unexpected potential cost since I didn't foresee myself needing. Due to budget issues I will most likely find a Elmarit vs a Summicron.
Processing time. I spend less time processing files from the M8 than I did with film. Not having to scan negatives, spot them for dust, and then do editing saves a ton of time. I would say generally I spend about 30-60 minutes per file from the M8 that makes it to print. Compared to 2-3 hours per file if I was scanning film on the Imacon and then editing for print.
1. M8 - $2000ish with original accessories, two new batteries $260, UV/IR filter about $60 each. - CLA on the camera will run upwards of $500. M8.2 upgrade prices are nuts. I just spoke with Leica NJ last week about it. Not worth it in my mind. I can forward you the price list if you would be interested in taking a look.
2. Lens - I think others nailed that one.
3. Apple iMac or MBP - $2000-2500
4. Lightroom $80 and Photoshop CS5 upgrade $200 (assuming all is legit with CS2)
5. Time machine - 2 TB Hard Drive with FW800 - $250 macsales.com (I buy all my hard drives though them)
Hope this helps some.
rutter.