Radeon 9000 issue:
It's typically hard to get a normal card to run at 15kHz in games(first you have get it running at 15kHz in Windows), you need an additional program to lock down the refresh rate so that it isn't changed by the game. I forget the name of the program.
ArcadeVGA:
What game are you intending to run? Most games should run fine on the ArcadeVGA, since you're pretty much limited to 800x600 (well there 1024x768 mode for compatability, but I don't think it'd look very good) at 60 Hz anyway.
Until Doom3 comes out you should be able to run most games at good speed at 800x600 on the arcadeVGA.