My build in progress. Started from tecmo34's thread and went from there. Special thanks to him, MadAdmiral and Proximon for advice. Green items are bought. Will update as I go if any better deals are found.
Notes: Not planning to overclock, so no HSF. A quick upgrade to the PSU would provide xfirex in the future. Went SSD because I already have 1TB for storage.
Actually, I lied in the OP...I'm NOT entirely set on 5850. I'm mostly going to be playing FFXIV and Starcraft 2 when they come out, which are far from demanding games by Crysis standards. I definitely want DX11 in there for the future, so do you think it would make more sense to drop down to a 5770 and save some cash? Would 650W support dual 5770's? Or should I just go with the single 5850, which would last longer on it's own anyway?
If it makes any difference, I'll be getting a 1920x1080 monitor.
I'm going to correct somethings to start with. Dual 5850s don't need 750W to run. ATI recommends a 600W unit with 4 PCIe connectors. The problem is that most 650W units only come with 2 PCI connectors, making them sufficiently powerful to run dual 5850s, but you'll need to buy some adapters (though 5850s might come with some). That's why it's generally recommended that you get the 750W units, since they will almost always have the required 4 connectors.
@Valoric: The 5870 doesn't cost $600. It costs $390 (outside of combos). Dual 5770s will run $300, but use up an upgrade path, use more power and generate more heat. It's advisable to go with a single card to start a build with. Dual 5570s will defintiely run on a 650W unit.
On to the build. Here's a couple of recommendations. First, I'd drop the i5 down to the X4 955 and a Gigabyte GA-790XTA-UD4. That'll generally save $100 and cost you nothing in terms of performance. Also, you preserve an upgrade path for the CPU, as the LGA1156 socket is going away in the next year, while the AM3 socket is sticking around for a couple of more years. That would either allow you to either upgrade to the 5870 (which you won't need) or just save some money.
Since your getting a 1080p monitor, I'd definitely stick with the 5850. It'll be powerful enough to play almost everything at that resolution, so you won't have to worry about needing more power if you get into other games.
I'd also consider switching the case/PSU to either the Antec 902 and Earthwattts 650W ($145 after rebate) or the Antec 902 and TruePower 750W ($190 after rebate). The 300 Illusion is a great case, but it's a little small. It won't really affect the components, but I always like to have a little extra room.
Allowing for the rest of your system and a healthy margin you are still good with a quality PSU that delivers around 50 amps of 12V power. In fact, that would probably be enough for CF 5850, but as Techmo says I wouldn't personally recommend that.
Great feedback, thanks a lot. Also thanks to all others who've replied so far, such great help on these forums.
Your CPU/Mobo advice looks sound (x4 955 w/ gigabyte ud4), so I'll probably go that route.
I'll also probably go single 5850 with the Antec 300 + 650W combo. The other case looks good but I'm more partial to less bling actually, and the 300 is cheaper.
I don't plan to overclock or xfire anytime soon, so I should be good with that PSU right? Can I also skip the heat sink in that case? The 300 has plenty of fans, but If heat sinks are recommended regardless, I'll definitely get one.
You should be fine with the Earthwatts 650 if you're not overclocking. You can skip the aftermarket heatsink until you start overclocking. The other benefit of an aftermarket heatsink is that they are quieter, so you may want to consider it if the stock cooling is too loud.
I thought the only benefit really of HDMI over DVI is built-in sound. I thought picture quality-wise, they are equal, no?
Also... this 470 + Windows combo is the same price as the 5850 if you're willing to deal with the power difference.
A 650W would still work, but would cut it close. Newegg's PSU calc is saying the system would require 608W with a 470 rather than 525W with the 5850... although I know these calculator's aren't perfect at predicting. But, no cost difference from a 5850 to a 470 is hard to pass up. Either way, a 5850 is a great card.