SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: casual gaming, some programming for school, watching movies, surfing the internet
PARTS NOT REQUIRED: keyboard, mouse, monitor, speakers, OS
PREFERRED WEBSITE(S) FOR PARTS: newegg.com, wherever's cheapest
COUNTRY OF ORIGIN: US
PARTS PREFERENCES: I was thinking of getting a Core-i5 760
SLI OR CROSSFIRE: Maybe
MONITOR RESOLUTION: 1920x1080
ADDITIONAL COMMENTS: This is my first build. I don't need to play the latest games on the best settings, although better would be nice. I'm willing to spend a little more if it's worth it. I can get the Core-i5 760 at Microcenter for $185 after tax
I don't keep up to date with newegg.com for deals and things (there are better places for us up here in Canada), but here's the parts I'd recommend... Should be pretty close to your budget.
MSI P55-GD55 motherboard (or buy an SLI one if you want to go that route in the future)
4gb GSkill Ripjaws RAM (I use the Red 1600mhz CAS9 stuff a lot)
GTX 460 768mb video card (1gb one is nice too if you want to spend a few more dollars)
550w-ish PSU (those BFG ones are cheap since they went out of business)
Case of your choice (Antec 300? etc)
1tb hard drive (or whatever you'd like)
I've been recommending that sort of setup for a few of my recent builds, and it ends up working out very nicely. That 460 will keep up with most games as well, and if you picked up an SLI motherboard you could always add another one in later on as well.
I'm not sure I'd buy MSI yet, but I suspect they have improved a lot since all the old horror stories. Not sure; some still won't buy them, but others do. Asus and Gigabyte get a lot of recommendations.
If that's the old BFG PSU, then oh no. Choose a PSU with full range active PFC (no little voltage switch) and 80+ certification. Antec, Corsair, Seasonic, Enermax, and the new XFX are among the better brands. For a single GPU up to a HD5970 or GTX460, 500W is enough; a HD5970 or GTX470 needs 550W, and I believe the GTX480 needs 600W (insane, imho). Add another 100W, 150W, or 200W respectively for multiple GPUs.
Before shelling out for a GPU though, what do you mean by "casual" gaming? If you mean low-demand titles (Flash-based games, Unreal Tournament, Guild Wars, WoW, Diablo II, etc) you could get by with a HD5750 even at your resolution. If you mean titles like Crysis, Metro 2033, or Stalker, then even a HD5870 won't let you max everything. Check some benchmarks, and consider what settings you may be willing to lower.
MSI boards aren't 'bad,' but yes, I'd personally take a Gigabyte over an MSI if they were similarly priced. What I use myself is an EVGA P55 FTW, which is another company I'm a fan of. That board, as well as the P55 SLI from EVGA have some juicy rebates at the moment too...
Since you mentioned an SLI board, you could look at getting something like a Corsair 650w PSU as well if you wanted to be able to just add in another video card.
Last but not least, yes I'd grab a 460 over the 5770. They are quite a bit more powerful to begin with, plus, if you did add a second one in the future - they scale super well (meaning doubling the cards is closer to doubling the performance).
I buy from NCIX.com most of the time - they usually have some free shipping offers with their weekly sales, plus, they offer pricematching from other Canadian websites. Use that + pricebat.ca or something similar, and you can get yourself the best of newegg, tigerdirect, and all the other sites out there.
Doesn't make much of a difference, but I'd be tempted by the 1gb version. It runs at 715mhz instead of 675 as well, and has a little bit of an overclock on memory also. Either way is great though, good luck!