umm maybe 415... lets see 1.8GHz sempron with a half gig of ram... C2d @ 3.3GHz 2Gb high performance ram... a video card... so far I have about 400% on the CPU, 400% more ram, and something in the area of 1000-5000% on the GPU. I will say though that there are certainely points of diminishing returns when spending more than say 1200-1300 or so. only point where you'de be getting around 15% more performance would be drive speed, and then just general useage, say browsing the net or using MS word. those are both more end-user limited in 'performance' than anything else though and for the most part performance diferences would be minimal and imperceiveable so I will agree on that. If you seriously think you can Run a game like Oblivion well on a 300$ system you're way off. you might be able to play it on the very lowest settings. also you spelt 'the' wrong... will say that I am a bit of a hipocrit for pointing such out though as I often typo as well.
just compare based off benchmarks. The lowend of ATI sucks... well guesse what so does the low end of nvidia. performance wise they are quite close at stock and post OCing ATi tends to pull in a lead. only reason I am saying go ATi is because they offer a real world physics solution. independant studies have shown that using ATi's GFX cards as a GP-GPU is about 10 times(YES 10) as effective as compared to when nVidia tried. then add two x2800s in CF and you're good to go... insane...