$900 build for gaming...Advice please!

E7200 Wolfdale 2.53GHz $120
GIGABYTE GA-EP43-DS3L P43 MB $90
WINTEC AMPX 4GB DDR2 800 (PC2 6400) RAM $65
SAPPHIRE Radeon HD 4870 video card $275 plus $20 rebate
WD Caviar SE16 WD6400AAKS 640GB SATA HDD $80
SAMSUNG 22X DVD Burner with LightScribe $28
Antec Sonata III w/ Antec Earthwatts 500 PSU $130 with $50 rebate
Vista Home Premium SP1 64-bit $100

Total $888 with $70 in rebates

Here's a list to give you some ideas:

Antec Sonata III 500 Black 0.8mm cold rolled steel ATX Mid Tower Computer Case 500W Power Supply - Retail $130 - $50 MIR = $80
This case/PSU bundle is a good deal for quality parts. You can also shop for a PSU and case separately.

GIGABYTE GA-EP45-DS3R LGA 775 Intel P45 ATX Intel Motherboard - Retail $127 - $20 MIR = $107
Good brand, good chipset, good overclocker, and has everything you may need.

PALiT XAE/48500+T352 Radeon HD 4850 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail $170 - $30 = $140
This is the least expensive HD4850 card on newegg. The HD4850 is the graphics chipset to look for these days.

Intel Core 2 Duo E8400 Wolfdale 3.0GHz LGA 775 65W Dual-Core Processor Model BX80570E8400 - Retail $170
Very fast dual core intel. If you can stretch another 20 bucks, get the E8500 instead.

pqi TURBO 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory Model PQI26400-4GDB - Retail $63
The least expensive DDR2-800 4GB kit with heatspreaders, decent brand.

Seagate ST3640323AS 640GB 7200 RPM SATA 3.0Gb/s Hard Drive - OEM $90
Seagate's latest, 32MB cache, large enough to last a while, 5-year warranty

LITE-ON 20X DVD±R DVD Burner Black SATA Model iHAS120-08 - Retail $29
Least expensive SATA drive, retail comes with decoders and burning software.

Microsoft Windows Vista Home Premium SP1 64-bit English for System Builders 1pk DSP OEI DVD - OEM $100
64-bit will use all of the 4GB RAM and allow more in the future.

That all comes to $879 before S&H, but also before $100 mail in rebates.

*EDIT - WR2 beat me to it!

*EDIT #2 - great minds think alike, eh?

I had also chosen the E8400 and GIGABYTE GA-EP45-DS3R until I found I was ending up over budget. The EP45-DS3R would be the first thing I'd upgrade if you want to spend the rebates before you get them

So I cut back a bit on the CPU and MB to keep the 4870 in the mix. The E7200 will OC to 3.0Ghz on the stock Intel HSF but to be honest in most games the 3.0Ghz won't make as much difference as the ~20-25% difference the 4870 has over the 4850.

pqi TURBO and WINTEC AMPX RAM are a good value for performance RAM. AMPX was in this THG review: DDR2-800 Goes Gold

With the Sonata case and PSU, might as well get the free X2 5400+ and sell it or give it away.

I would go with the E7200 and get a 4870; since this rig is mainly for gaming, the 4870 will give it more longevity and he can upgrade to a quad when they're cheaper and more relevant.

Considering that Sonata practically comes with a free 5400+ BE I would build the system off of that so you can get a 4870 instead of a 4850.

This motherboard works with the 5400+ for example.

GIGABYTE GA-MA770-DS3 AM2+/AM2 AMD 770 ATX $79+9
http://www.newegg.com/Product/Prod [...] 6813128081

Edit: the E7200 is a little better than the 5400+, but of course it's not free. The E8400 is a lot better. You can see some benchmarks here:
http://www.tomshardware.com/charts [...] V,389.html
The 5400+ and E8400 are there. The E7200 is not, but look at the numbers for E6600 because they are very close to the E7200.

The motherboard is 1600/1333/1066/800 compatible.

GA-EP45-DS3R website

The E7200 is 2.53Ghz which works out to be a 266.5Mhz FSB (1066 quad pumped) times the 9.5 CPU multiplier.
If you overclock the E7200 to 333Mhz FSB (1333 quad pumped) times the 9.5 CPU multiplier you'd have a 3.16Ghz CPU (roughly E8500 equivalent)
This would be about the max OC you could expect with the stock Intel C2D HSF. A good E7200 can reach this speed without extra vCore increase.
Taking the OC to 400Mhz FSB (1600 quad pumped) times the 9.5 CPU multiplier you'd have a 3.8Ghz CPU which is a bit more than 50% OC.
E7200 review