Well, to put it in simple terms, any ATI Radeon 7500 card should give you the ability to run two CRT monitors, this same applies to ATI Radeon 9000 and Radeon 9000 Pro. Some of the less expensive Radeon 8500s (the LE kind) have the support for the second simulaneus CRT chopped off, but you should be able to pick up Radeon 8500 with a full CRT support for around $110.00 for sure (if aanyone knows which less expensive Radeon 8500 cards do support dual CRT config, let me know).
The reason I am insisting about 8500 is that it is much faster than 7500 and faster than 9000 and 9000 Pro.
To simplify this even more, you would need only one AGP Radeon mentioned above to be able to play with dual CRT. ATI gives you excellent multi-monitor/multi-desktop managment software called HydraVision, and it is available for download off the ATI web site.
The Radeon 7500 can be picked up for as low as $60.00, but you may have to get a DVI to regular VGA converter for additional $10.00.