There's no such thing as a 650c wheel for CX bike. Just no tires. 650c tires come in only slick, and either narrow (23c) and narrower (19-20c)--although Terry offers a medium quality 28c 650c touring tire made by Panaracer.

There are 26" wheels and some CX tire options (Schwalbe makes a decent one that is 26 x 1.35, good and legal for CX). I wish there were better and more varied options, but there aren't, yet. For my opinion regarding the rest of your question, I'll stick to this:

http://forums.teamestrogen.com/showthread.php?t=36861