Out of those, I think the Carr Slant 6V is my favorite, although I don't know much about the Sewell. I also like the 6V more than most other Carr models. It's one of the best sounding 6V6 amps I've heard.
Hoss, another amp that might be less expensive, that's surprisingly good is the EL-84 Hughes and Kettner 20W. It's got a nice gain channel and sweet EL-84 chimey clean channel. Less than half the price of a Shiva.
http://cgi.ebay.com/Hughes-Kettner-...376528632QQcategoryZ10171QQrdZ1QQcmdZViewItem