Post some pics of the bottoms. I have been able to repair some really nasty water damaged cabinet bottoms before. That way you will end up with 2 usable cabs, so you can sell one to pay for the other.
If they are really bad, what I normally do is strip the sides down to the bottom and build a false bottom out of 1x3's and a 1/2" plywood or particle board bottom then mount the new bottom on with liquid nails and some screws. Next bondo the sides to smooth the join, rasp and sand the joins smooth and prima and paint.
If the are just rough, then I will build the overhang on the bottom up with bondo and put a piece of aluminum channel molding or l-bracket (painted black) on the outside to hide the rough edges.
There are some pics in my photo album showing the aluminum bracket fix on a Moon Patrol cabinet (link: http://forums.arcade-museum.com/album.php?albumid=62). There are a couple of photos of replacing a Galaga bottom with a new base board.