hehe, after reading this trough I'm quite set on the sennheiser 280 pro's, never heard anything bad about them and I need a really good isolation, I hate it when I still hear my amp even when I have my (übercheapass) headphones on.
I've got the nano head for two weeks now. The tubes are meant to last forever (mister Z. Vex can be contacted at the forum www.zvex.com) but you can buy replacement tubes at his site, and the customer service is incredible! I don't really understand the thing with the aligator clip, I saw that too in the mike thompson movie, but my amp doesnt hum AT ALL, not even at highest volume, ... I use humbuckers, no single coils though. Currently I'm using the cabinet from my vox ad60vt amp, but it lacks alot in the low end, I'm thinking of buying a 2*12 greenback cabinet, probably an orange, I'll cost quite much but I'm not sure how much.
the zvex is a .5 watt amp, it's got a 2" speaker, but that's more of a joke. If you want to get a good tone you'll need a cabinet, you don't need a bit 4*12 (although it's possible) maybe a small 1*12 cab will do, or even a 1 * 10.
People are not too happy with rocktron, but if your fave artist uses it ... it might be good to try it out your own, you never know what they did to the mix to get that awesome tone. I don't recommend it, but I won't say you shouldn't get it.
I recommend ENGL screamer, 50watts of sweet tones. With it's 4 channels it's got everything you will ever need to rock! It's built like a tank too, so you won't have trouble loading it into your car when you want to play in a band. The cleans AND the distortion sound is totally awesome. Its also got reverb, it's probably the only effect that really need to be built in the amp to sound good. You can also get a seperate footswitch if you want to go gigging alot.
Oh sorry, I didn't see your price range, but the zvex will be in your range and if you get a good cab with it you'll never buy another tube amp, the only problem might that you'll have to mic the cab for giging.
+ not to forget, alot of layering is done to get that really smooth tone. A big key to their sound is also the different 4 * 12 cabinets that are used + mic positioning on the recording to get those punches in the low end. And for some stuff I even heard bob rock say he placed the mic behind the amp to get an even darker sound. But as said, the tone comes from the mesa's.