Erm.. Thanks for help, but I already know it
It's not like it's going to fry graphic card either, system will just be stable or not.
I'm asking for personal experience to save me from mess of buying/selling cards that will not cut it.
Nonetheless, thanks for time and insight, on other board I was spammed by "Buy ATI", "Buy GeForce3", "FX series card will not work on AGP 2X board", and other replies completely missing the point.
(ATI never made a card withstanding AGP overclock, furthermore there is no drivers for FreeBSD, GeForce3 was very AGP speed sensitive, and FX series cards works fine in AGP 2X slots.)