how much euros are you willing to spend ? based on that, we could suggest alternatives with better price/performance ratio.
edit: in german stores I find prices for a 128 MB Radeon 9800 Pro of at least ~ 180 euros. The 256 MB models are totally overpriced.
Now if you're gonna go for a 128 MB card (256 MB models definately have an advantage in future games IMO), I would suggest you the GeForce 6600 GT for AGP really, it costs about 220-240 euros but the performance increase over the 9800 pro is quite big. In particular, the XFX 6600GT AGP (XFX is a manufacturer) is supposed to be a good card because of the memory chips they put on it, very well overclockers. I think that card is listed for about 220 euros here. The only downside of the 6600GT is the 128-bit memory interface which certainly is a bottleneck for that card, seeing as there are 256 MB versions of it expected (currently only 128 MB ones are available). However, the 9800 Pro also "only" has 128-bit interface, but back then that was top of the line.
Now alternatively you could spend some more and go straight for a GF 6800 series card, which has the advantage of a 256-bit interface and the chance of unlocking extra pipelines on the non-GT/Ultra models (if your system is AGP, not PCI-E). Apart from that, there are more models with 256 MB memory in that sector of cards.
Dont bother with the Radeon 9800 XT btw, its just an auto-overclocking 9800 Pro with 256 MB and is really overpriced for the minimal performance improvement over the Pro.
If you're an ATI-only customer, you can only have the 9800 Pro/XT or go straight for the X800 series which cost a lot more (and the X800 Pro is overpriced compared to the GF 6800 series). They havent released AGP versions of the X700 models, and your system is AGP I guess.
Hope that helps.