I read it. By one benchmark:

http://www.videocardbenchmark.net/

The A10-7800 is considerably better than the GTS 8600. Proves nothing about the performance in specific games.

Why not try it?...

Good point.

I'm accustomed to think of integrated graphics as poor, but a) that is less true for the AMD APUs, and b) the GTS 8600 dates from 2007.

Short version: no.

However, the GTS 8600 card probably has DVI-I output(s), so you could use a DVI-to-VGA adapter to plug a VGA cable into the nVidia card.

It's just a passive adapter, so it's...