Ron_forrester,
The others have given good advice. It really does depend upon the rig, and also upon the era it was constructed. You didn't mention if you're looking for used or new.
I remember when we were doing our research back in 2003/2004, the Fourwinds 28A or 28D models, which didn't have slides, had about 2,800 lbs. of cargo carrying capacity. We were a young family of 6, with dogs, so we knew we needed the CCC. Unfortunately, without slides, it didn't have the interior space we desired. I figured that with our family, we would need just about 2,500 to 3,000 lbs. of CCC. The Class C's with slides of that era just didn't offer what we needed.
Also, keep in mind the the CCC number by itself is a bit misleading. There are individual axle weight limits which also need to be respected. On many Class C's, you'll reach the rear axle weight limit before you reach the GVWR (related to CCC). In other words, part of the CCC number is generated by the load capacity of the front axle, but it's hard to load the rig to add weight to the front axle. In fact, anything you put behind the rear axle unloads weight from the front axle and adds it to the rear axle.
We ultimately decided to go with our 36' dual slide Class A in our signature which provided the space and weight ratings we figured we'd need. "Super C's" were not very popular then so they weren't really part of our research. But now they are.
If you find yourself needing more space and weight capacity than the typical C's offer, take a look at the Super C's, as well as some Class A's.
Good Luck in your search,
~Rick
2005 Georgie Boy Cruise Master 3625 DS on a Workhorse W-22
Rick, Gail, 1 girl (27-Angel since 2008), 1 girl (22), 2 boys (23 & 20).
2001 Honda Odyssey, Demco Aluminator tow bar & tow plate, SMI Silent Partner brake controller.