I'm considering replacing my 8500GT with this http://www.pcgarage.ro/placi-video/leadtek/winfast-gts-...
My display resolution won't go beyond 1280x800... I can't seem to find a review of this specific model (version 3)... I tend to think that GPU's that have the low power tag don't perform pretty well in games
The PSU is a bit tight. Have you considered a 4850? A great card for that PSU, and for that resolution. Alternatively, you could go with a GTS 450 (might be pricey) as I'm running it fine on my 400W, just check you'll have enough Amps.
Overall, I'd say a 4850 would be a solid recommendation.
The 450 isn't a bad card despite being 128bit, it does have DDR5 ram which is very quick. I can game on very high resolutions with all settings high, so for me it's a great GPU. The 4850 and the GTS 250 perform about the same, so you can go for whichever is cheapest. You'll see a massive increase over your current card either way!