If you don't have a Microcenter nearby, and saving money is important, I recommend using Bing Cashback (www.Bing.com). It's super easy to use. I did with my build, and I'm in line to get about $80 in cash back. You have to wait 60 days for your money, but it's legit, and it's green. Tigerdirect/CircuitCity/CompUSA all qualify for 8.3% cach back with Bing everyday, and every couple of days, one, or all three sites, will jump up to 15%, or even 20% on an odd occasion. I used BCB on my Radeon 5850, and got 8.3% off of $299, for $275, with free shipping. So I saved $25. Did the same with my i5 processor.
Also, Ewiz.com gives you 5% off with Bing. Newegg sometimes nets 1 or 2%. Zipzoomfly.com 2-5%. It adds up, especially with Tigerdirect purchases.
Anyhow, back to the build. Remember, I'm trying to stay with lowest price possible, without picking absolute trash for components. You can get some cheaper components, but these are about as low as I'd go.
You could probably save a few bucks with a micro-ATX board, and opting for some components with rebate offers. Also, I'd really try to go a step up from the 5770, to a 5830 or 5850. The 5770 can leave a lot to be desired. Moving to a 5830 would add about $80 or so. I did not include a monitor. Prices change on those everyday, and there are a million places to find deals on them.
Like another poster mentioned, an AMD build might save you some money.
Change to the AMD Phenom II X4 955, and then a crossfire capable mobo with SATA 6Gbps for under $150. And that should go a way towards paying for a 5850, without increasing the price too much.
I haven't seen the evidence for the 5770 being weaker at higher resolutions. Altho it makes sense.
Personally I think the only threat Fermi will pose will be from the usual fanboys jumping on it, nothing I've read suggests that Fermi will be particularly useful for gamers, considering how strong ATI's 5000 series is. But then it is possible that you would regret it when they came out if you bought before release. Also you give more of a chance for Lynnfield parts to go down in price or failing that for 890GX boards to mature a bit.
The 5770 won't run some of the latest games at high settings. When it does, some complain about the performance. Prior to building my unit, I was considering a 5770, and no matter how much I hated spending over $100 more, all my research told me to stay away. If you crossfire two, well then you're better off buying a single 5850. Performance wise, the 4890 beats the 5770. The only real measureable quality the 5770 has, is Dx11, and Eyefinity technology. The 5770 will be ok, but if you want your system to perform, and perform well for a few years time, invest the extra money in a 58xx series card.