About the video card is up to you, really there is no way of going wrong with 5870's though if you want to wait is up to you, I wound't.
Same thing for the monitor really there is no way of going wrong with a UltraSharp monitor.
Yes a quality 850w is more than enough to handle 5870's.
Build the computer if the sound is good enough for you don't buy a sound card if you think the sound is bad buy one, usually now days the onboard sound is already really good.
Yes probably price of Blu-ray burners will be coming down, though I wouldn't spend money on one unless I needed to burn blu-ray discs, which I really don't know many that need it.
Agreed on not going with 2x 5780s. If you really wanted the GPU firepower now, you could always opt for a 5970 and save a PCIE slot.
I'll have to disagree with your choice of HSF, which is hard to say since megahalems have been king for awhile . I suggest looking up Thermalright's Venomous X or a Noctua NH-D14. The venomous x is slightly more expensive than the megahalem/mega shadow; the d14 having a ~$25-30 premium. However, my reasoning is that if you don't plan on watercooling your $3000 system, you might as well opt to get the best-of-the-best HSF. Both of these contenders offer better performances for the min/max'er. I don't know whether you'll have clearance with the d14 and your mobo/doms, but the venomous x is a sure thing. (Also a side note with the venomous x... the thinner frame usually gives enough room for 38mm panaflos or san ace h1101 [regarded as the premiere fans for static pressure] fans if you'll looking for a true min/max on your cooling system.)
This ties me in with my next suggestion. Regardless of what HSF you choose, consider Gentle Typhoons over your s-flexes. Nothing wrong with them per say, unless you count the pretty horrid sound it takes at 12v (to be fair, this is a personal judgment call) but the GTs (ap-15 specifically) perform slightly better, are noticeably more quiet, and the sound it makes at 12v is less of a jet engine and more of a hiss, (also judgment call) so take that into consideration. Regardless, both provide excellent static pressure.
Thanks for the suggestions! I changed the HS to a Noctua NH-HD14 in lieu of the Megahalem.
Is I go with the the 5970, do you think I should go with a 1000W+ PSU in case I want to get another? Or do you think by the time I need additional performance, a better single board solution will be available?
Also, is the 80GB Intel X-25M the best SSD drive at the moment? Thanks!