I've got the Valveking head, and I run it through a 5150 4x12 Cab. I also replaced all the crap EH preamp tubes with 1 (Regular) JJ ECC38 1 JJ High Gain ECC38s and 1 Tung Sol ECC83. (Will replace the poweramp tubes when I have the $$...the Ruby tubes are Ok, but I want to try something else) It is a very good amp for the money. If you tweak it right, you can get some killer tones out of it. It also REALLY likes Seymour Duncan Custom 7 humbuckers. Another alternative is finding one of the Peavey Windsor heads, which basically IS a JCM. They sell used for around $200 now, only one channel, but a killer amp for the money.
I recommend you get the VK head over the Combo. A buddy of mine has the 2x12 combo, and I could not get a good tone out of it, on the other hand...I can get great tones out of mine. Of course it doesn't stack up to a 5150, or ENGL, or Mesa. But it is indeed a great tube amp for the money.