nope only the 97/9800's will support ALL of DBPro's features
remember you have to include the shader & effect support into all of this.
and from what i can gather thier support with the .fx are apparently limited, not tried so can't varify.
the differnce between the AGP rates only comes into play with larger memory requirements. for example when using FSAA on scenes over 1024x768x32 at AGP2x FSAA4x lets say Q3 will run at 75fps (which is about right for the FX5200 w/600mhz P3), well at AGP4x you can sequeeze an extra 5fps and AGP8x almost 12fps extra.
However for that kind of performance difference you'll really need a processor running 3DNow!2 and/or SSE2 as well as memory runnning at or above 266mhz+ (or double the FSB for the motherboard)
else it makes no odds really, and on the top end cards with over 128mb ram again unless you have intensive games running like Half-Life2 or the nVidia demos' your really ot going to notice much of a difference.

that said though the FX5200 isn't a slouch, there are alot more expesive cards which can not keep up with it speed wise.
G5x0, SiS680, Kryo2, Radeon 90/9200 are good examples for DirectX.