Replacement options - need advice

well...to recommend you a card, I need to
-know your system specs (detailed)
-Know what games you plan or do play
-know what resolution you play at

-These things, I must know to recommend you the best card  

Sure thing, here is the machine I just built:

COOLER MASTER RC-690-KKN1-GP Black SECC/ ABS ATX Mid Tower Computer Case
ASRock X58 Deluxe LGA 1366 Intel X58 ATX Intel Motherboard
PC Power & Cooling Silencer PPCS750QBL 750W ATX12V / EPS12V
Intel Core i7 920 Nehalem 2.66GHz LGA 1366 130W Quad-Core Processor Model
OCZ Gold 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Triple Channel Kit Desktop Memory
XIGMATEK Dark Knight-S1283V 120mm Long Life Bearing CPU Cooler
Western Digital VelociRaptor WD1500HLFS 150GB 10000 RPM 16MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive
2 X MSI NX8800GT 512M OC GeForce 8800 GT 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card
(i should make this my sig)

I mostly play MMO's, specifically Everquest2, but I also enjoy some FPS like Left 4 Dead and Fallout 3.
I play on a 24" monitor at max res (1900x1200)

Thanks for the help.

Hmm...So assuming you play 1920x1200 I would recommend personally getting a single GPU as it is more reliable and stable. For that resolution and based on your games I think a GTX275 would do that job

i too game on a 24inch screen, it depends if you like to play with AA and AF.

personalty I would get HD4890 as here in the uk at least tehy are alot cheaper than the GTX275 and can bite a GTX285 if overclocked

+1 GTX275.

If you get the right GTX275 it will be faster than the HD4890.

so much for branded makes no differences  

If you want that extra AA and AF enabled on the more consuming games then get a factory overclocked GTX275 or just get GTX280.