Seems the last card on their list can be SLI'd for a quad card performance?
From Elder's Scroll's
Rock Bottom (these cards do NOT support pixel shaders, and as such, won't run Oblivion)
* (Any integrated graphics that's NOT listed elsewhere on here, save for any integrated Radeon or GeForce chips I forgot)
* Radeon 7000 (Radeon VE)
* GeForce 4 MX 4000
* GeForce 256
* GeForce 2 MX
* Radeon 7200 (ATi Radeon)
* GeForce 2 GTS
* GeForce 2 Pro
* GeForce 2 Ti
* GeForce 2 Ultra
* GeForce 4 MX 420
* Radeon 7500
* GeForce 4 MX 440
Outdated (these cards support shader model 1.x, which at the very least won't enable HDR in Oblivion, or may only allow diminished features, or may not even run the game)
* Volari V3
* GeForce 3
* Radeon 8500
* Matrox Parahelia 128
* Radeon 9000
* Radeon 9100
* GeForce 3 Ti
* Radeon 9200
* Radeon 9250
* GeForce 4 Ti
Low-end (these cards support shader model 2.0, but are fairly old now)
* Intel GMA 900 Integrated graphics (chipset 915) (much better than the "Intel Extreme," but still somewhat below a GeForce FX 5200, and perform more like the "outdated" group)
* GeForce FX 5200 (questionable SM 2.0 ability)
* GeForce PCX 5300
* GeForce FX 5500
* GeForce FX 5600
* S3 S8 256
* GeForce 6100 IGP (integrated graphics)
* Radeon Xpress 200 (integrated graphics)
* GeForce FX 5700
* GeForce PCX 5750
* Radeon 9550
* Radeon X300 HyperMemory
* GeForce 6200 TurboCache
* Radeon X600 HyperMemory
* Radeon X300SE
* Radeon 9600SE
* Radeon X300
* Radeon 9600
* GeForce 6200
* Volari V8 Duo
* Radeon 9500
* Volari V5 Ultra
* GeForce 6600LE
* GeForce 6500
* Radeon X1300HyperMemory
* Radeon 9600pro
* Radeon X600pro
* Radeon 9600XT
* Radeon X600XT
* Radeon 9500pro
Mid-Range (these cards were/could've been considered top-end a few years ago, and are fairly powerful, using 8 pixel pipelines and support for at least shader model 2.0)
* Radeon X1300
* GeForce FX 5800
* Radeon 9700
* GeForce FX 5900XT
* GeForce FX 5900
* GeForce 6500
* GeForce PCX 5900
* Radeon 9800
* GeForce FX 5800ultra
* GeForce 6600
* Radeon 9700pro
* GeForce 5900ultra
* Radeon 9800pro
* GeForce 5950ultra
* Radeon X700
* Radeon X1300pro
* Radeon X700pro
* GeForce 6800LE
* GeForce 6800XT
* GeForce 6800 (PCI-express version)
* GeForce 6600GT
* Radeon X800GT (also called X800RX)
* Radeon 9800XT
High-End (some of these cards may be "outdated," but just about any given one is OVERKILL for almost any game out there)
* Radeon X800
* Radeon X1600pro
* GeForce 6800 (AGP version)
* Radeon X800pro
* Radeon X800GTO
* Radeon X1600XT
* Radeon X800GTO²
* GeForce 6800GS
* Radeon X850pro
* GeForce 6800GT
* Radeon X800XL
* GeForce 6800ultra
* Radeon X800XT
* Radeon X850XT
* Radeon X800XT Platinum Edition
* Radeon X850XT Platinum Edition
OMGWTFBBQ! (these cards are outrageous; a new top class all of their own, they are rather expensive, but insanely powerful. Note that I cannot guarantee perfect accuracy of this ranking)
* Radeon X1800XL
* GeForce 7800GT
* GeForce 7800GTX
* Radeon X1800XT
* GeForce 7800GTX 512mb
* GeForce 7800GT Dual (a pair of cards on a single board; can use a pair of these in SLi mode)