Generally:
Big gigs - big drums
Small gigs - small drums
Normally larger, thicker shelled drums project more.
A big exception is if you're mic'd up. Then pretty much anything goes.
I saw a guy using a mic'd up 16" bass drum at a fairly large outdoor concert.
If you didn't look at the drums, you'd never know it.
PA's and EQ's can work wonders.
You can really use any drum set for anything. Sometimes you'd have to find workarounds though.
About the Stage Custom bop kits. I've had a couple of them.
They tune up nicely in the middle and upper ranges, and the stock heads they come with sound pretty decent.
And Bo - I think he meant he'd save some money by trading in, not get some money, even though he phrased it differently.
I suppose it's possible, but hard for me to imagine trading a Safari kit for a SC bop kit and getting cash on top of it.