I am basing this post while playing through an Epi LP Elitist Standard Plus with the stock P/U's which are similar to Gibson 490's. I've owned most of the amps already disussed.
The JSX is way too expensive and is not warm at all but has a great ultimate overdrive the clean is too clean and the crunch is just crunchy.
The B 52 AT 100 combo has a great rectifier sound for around $700. It just isn't warm enough on the clean channel and the eq's are pretty lame. But for $700 it will Shredd with any Mesa. It does have some reliabilty issues.
If all you need is Rectro sounding distortion then the B 52 is as close to $500 a that I could find. You could pick one up on ebay but it is so heavy that shipping will kill you.
I played through a V 30 Palomino 1x12 as the only guitar in the band and could always be the loudest if I wanted to. The 30 watt has el 84's but you can get one used for about $300 easy. The EL 84 do have a bit of rattle at high volumes but you'll only here it in a studio or bedroom. This is because the 2x12 v30, the v-30 head and the v50 have been released.
The Palomino's sound good from the factory but if you buy a matched set of tubes from a company like eurotubes, the sound is the best I've ever heard. It makes the new Fender line look sad. I have tried a normal set and a high gain set. The high gain set of tubes sounds great although it isn't a rectifier sound more like Marshall or Hiwatt. I could emulate Pete Townsend perfectly.
I wanted more sound and haved tried to get the warm Fender sound combined with the recto sound in one amp. I went through 8 amps from guitar center last month, (they hate me there). I was up to the Marhsall JVM for $2000 plus bucks. I could not find anything to match the Palomino warmth. The guitar center guys all argeed that when I returned a $2000 amp that the Palomino sounds better. They jam with these things after the store closes. They hate the Palomino because there is no mark up on it, same with the b 52.
I just upgraded to the v50 and the 2 speakers are a big improvement. I still love to plug straight into the amp and just play through the clean channel, the dynamics and harmonics are phenominal.
Just rememnber, you can't get a good clean tube sound unless the amp provides it, the sound starts at the amp. I can always get good distortion with almost any amp as long as it has good speakers.
As for the Metal shredd sound, my Boss MT-2/chorus/delay/reverb do the trick pretty well. People are always impressed to hear that sound coming from a combo.
Check it out!