I upgraded a Visiontek Ti4600 to a 9800 Pro, but I dropped $300 in the process... the 9800 is MUCH faster then the GeForce.... BUT ... I only dropped the bucks because "Halo" looked like crap @ 800x600x32 (the highest res I could get decent framerates at)... now I can play at 1280x1024x32 at what feels like much higher performance & image quality.
The reason I threw in the "but" there is this... are you playing any DX9 games now, because if not I would just stay put for about a month
because unless your a 3d-mark freak or are playing one of the few DX9 games out there, you will save yourself about $100 by waiting & aside from "Halo" & 3D Mark 2001se, (3D 2003 is too DX9 reliant to use as a comparison) you will be underwelmed by the performance increase the
9800 pro will bring you, never mind one of the lower model cards.... sure Quake 3 picks up about 50fps @ 1600x1200x32, but who really cares?
BTW... don't even consider an FX 5600, in DX8 benchmarks it may well be slower then your Ti4200, at least in the benchmarks I've seen...the
jury is still out on the FX 5700 which is slated to be priced around $200 at release & by the time its IS released the 9800 Pro should be around
the same price.... either way you win by waiting & if it wasn't for "Halo" thats exactly what I would have done.