well acording to wikipedia the gpu specs in the ps2 are
# Graphics processing unit: "Graphics Synthesizer" clocked at 147 MHz
* Pixel pipelines: 16
* Video output resolution: variable from 256x224 to 1280x1024 pixels
which even the aging ati 8500 could easily beat spec wise but its really an apples to oranges type of comparison since even the best emulator will never be the same as the intended hardware.
so really what you need to learn is what people familiar with your chosen emulator think is required
What are the requirements for using this emulator?
* Windows/Linux OS
* CPU that supports SSE2 (Pentium 4 and up, Athlon64 and up)
* GPU that supports Pixel Shaders 2.0
* 512mb RAM
* Windows Vista 32bit/64bit
* CPU: Intel Core 2 Duo @ 3.2ghz or better
* GPU: 8600gt or better
* 1gb RAM (2gb if on Vista)
so based on those recommended specs im gonn guess that gaming on an ati 8500 with this emulator might be possible but i doubt itd be easy. looks like you might have to throw some newer hardware at it.