This may not add much of value after PFunk's comment.
I buy the cheapest reference design card the day I buy (I've had Sapphire, PowerColor, HIS recently).
If they are all selling at virtually the same price I would consider ASUS, Sapphire, Powercolor first.
You can go with an HD4890 as my HD4870 plays everything I throw at it -- with max or near max settings.
One advantage of going "cheap" now is that the DX11 games will be in full force by 2011 (only a year+ away). By then not only will the Nvidia G300 series be available, but ATI will have moved to its next major generation (the HD5xxx is the last of the current generation). Thus, one could upgrade then to an expensive card and have it last a good while. That's my plan -- if I can resist the temptation to upgrade that long

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ATI Crossfire Sapphire 2x HD5870 - Eyefinity 5760x1200 24", 1xDell-U2410 H-IPS + 2xHP-ZR24w S-IPS, Phenom II X6 1100T@4.0GHz w/Swiftech Water Cooling, 16GB GSKILL PC3 1866@1333, ASUS Sabertooth 990FX, WDigital + 3x Seagate + Hitachi + 2x WD Ext = 10.0TB, Sony DVD, OCZ ZX 850W PSU, CoolerMaster HAF922, TM Warthog HOTAS, TM T-Flight Stick X, TM Cougar+FSSB & CH Pedals, Saitek X52 Pro & Pro Combat Pedals, TrackIR5 w/TC Pro, Windows 7 HP 64b