Make sure the card will fit the AGP v1.0 slot....it is different from AGP2.0
and AGP3.0 slot. AGPv1 only supports 3.3V cards (most agp2/3 cards
(including newer ATI cards) require 1.5V) so get a card that can handle a
3.3V signal.
After a quick check at ATI website it seems that Radeon 9700 supports 3.3V
(9600 or 9800 do not) so that might be the card of choice for you. If I
we're you I'd get the card only if your retailer would be willing to refund
you in case the card would refuse to work after all.