Two differences that I'm aware of:
1) The Carver is a "pro gear" product, designed and manufactured for use in professional settings (recording studios, etc.), whereas the Solar was designed from the ground up to be a hi-end consumer product.
2) Price point. This is an educated guess, but you should be able to pick up a Carver Pro ZR1000 from Nathan @ Eighth Nerve for a little over one-third the price of the Solar integrated. For almost 3-times the price, you SHOULD hear a difference.
Undoubtedly there are many other differences, but these two came immediately to mind after reading your comments.
DU