I'm not too familiar with Carvin power amps but there are boatloads of cheap alternatives out there. I'm currently using an ADA microtube 200. It is a solid state but has 2 12AX7s with a presence control to give it some tube flavor. I got mine for $45. For other solid states, check out the Tube Works Mosvalve and Hafler also has a Mosfet Tube amp. Tube Works and Hafler both nailed the mosfet circuitry though Hafler's is a hair better. For tube, check out old Peavey power amps like the 60/60 or 120/120. Peavey is one of the few big name companies that you can get vintage amplifiers from for extremely cheap. They're always changing up models and designs and quite a number of them are gems.
edit: The Hafler power amp was the G300.