IF IT WERE ME, I wouldn't trade the Jazz unless you a) just really, REALLY don't like it or b) something is seriously wrong with it. The Fender J or P sound is one of those that can hold it's own in just about any (if not all) application and you never know when that situation may arise. I would keep the Fender and trade the Peavey for either one of the others. I liked the Warwick's tone when I played one, I've never been one for the way they feel. The frets always seem sharp and a bit long, could just be me. I've always liked Spector pretty well, can't help much as I've never played the Rebop, heard good things. What style(s) do you play? This could help to narrow things down a bit.
Again, this is just a IF IT WERE ME opinion. Whatever you think is best for you. If you really want to trade both of your's for both of their's, then go for it. Cool basses all around!