Reasonably priced upgrade to Dell OEM PCI-E Radeon X800...

The Dell PC that I'm using as my main FS system came with this card:ATI Radeon X800SE (a.k.a. dumbed-down X800 card) - 425mHz graphics processor 128Mb 800mHz SDDR RAM 256 bit memory bus 8 pixel pipelines 6 vertex processors PCI-Express interfaceWhen I originally bought this system last year, new in the box but from an individual, I planned to immediately upgrade the video card. But, after playing FS9, Doom3, and Half Life 2 on it, I decided that it wasn't such a bad card after all so I've been "living with it" for quite a while. It's actually held up pretty well for being a purpose-built OEM variation on the X800 line.Lately, though, I've been wondering whether a <$300 vid card upgrade might significantly upgrade the overall performance, and especially (of course!) FS9's performance.I am generally biased towards NVidia cards - I have them on 3 other (slower) PCs - but would not diss an ATI recommendation by any means... But, note that I'm not prepared to buy one of the $500 high-end cards, and also I'm leery of the "OC" overclocked NVidia cards that I've seen offered, mostly due to heat concerns.Other relevant system specs are: 3.4gHz Hyperthreaded P4; 1Gb RAM.What say youse hardware experts? Should I just stick with what I have? Thanks,Dave Blevins