I am upgrading from EVGA 7900 GS KO to 8800 GT. My short list is -
EVGA 512-P3-N801-AR 512MB, 600MHz/1800MHz shader 1500MHz
XFX PVT88PYDE4 Extreme 512MB, 640MHz/1900MHz shader 1600MHz (?)

I play FPS at 1680x1050. Both cards look like good deals. I am concerned about heat and noise. I have seen many forum posts about overheating 8800 GT. Will one of the cards be better for heat and noise than the other?

I've owned other EVGA video cards and like the company. I don't know XFX.

My case cooling is 120mm rear exhaust, 80mm side exhaust, 80mm front intake, and 120mm exhaust on PSU.

From the reviews that I have read the new 9600 GT may not be up to 1650x1080 in new games. The 9800 GT coming in April looks to sell closer to $300 than $200 at release. My budget won't stretch to include after market vga cooler. I expect to keep the new card for two years.

my pc specs are:
Intel C2D E6400 @ 2.66 GHz
GIGABYTE GA-965P-DS3
mushkin 2x1GB EM2-6400 @ FSB/DRAM 4:5 415MHz
EVGA e-GeForce 7900GS KO 256MB
ENERMAX Liberty ELT620AWT ATX12V 620W, 36A combined (2x22A)
Seagate Barracuda 7200.10 250GB SATA 3.0Gb/s, 320GB SATA 3.0Gb/s
SAMSUNG Black 1.44MB 3.5" Internal Floppy Drive
LITE-ON Black LH-20A1H 20X DVD+-R 48X CD-R IDE Burner with LightScribe
COOLER MASTER Centurion 5 CAC-T05-UB Black w/Blue Aluminum Bezel
SANSUNG 226BW 22" widescreen LCD monitor
Microsoft Windows XP Media Center 2005 SP2b - OEM

I dual boot Vista Home Premium 32bit OEM and figure I'll be primarily running Vista some time this year.

i dont think heat will be a problem. sounds like you have more than enough air flow. Have you considered zotac 8800gt? its the fastest oem 8800GT i believe.