Back-up..........back-up??? This could replace the Ampeg in a jiffy! Haha!
.........depending what tone you need of course!
Yes, the SC is the same as the 'non-overdrive' channel on the AG500. It is a 2-channel amp, one clean and the other is clean'ish to full blown drive. Check this clip to get an idea:
YouTube - In The Field With Stu Brooks from Dub Trio
First Stu's clean tone which is set quite low and Dubby, then the other with Massive drive.
The AG500 is really my favourite amp and has been for a few years even after trying a lot of others (see my profile for an idea), with the DB751 being a close second for different reasons. My humble opinion of course, but for €650 you could always sell it on for more if it doesn't work for you.
Cheers,
Andy