The Bass 400+ will always be my fav. However, I do understand the concern for your back.Reading about your back here made me put an asterick on my Bass 400+ recommendation: it's heavy!
Chisloe,
Mesa's other larger watt amps sound good in videos and get a lot of praise from the 400+ users who have both. These would be the Titan (discontinued I believe), Carbine 9, Carbine 6, and Big Block 750.
I would give the M6 Carbine a listen. Gobs of volume and a little easier on the back. I own one and I believe will stay in the stable for a long time (unless Mesa comes out with a Walkabout 600...).
Trace Eliott is another fav of mine. I used an AH1200 sm for years. If it weren't so dang heavy, I would probably still have it.
I just purchased a GB Streamliner and the jury is still out on this one. I think I have the wrong cabs for it.
I have heard real good things about the Aguilar Tonehammer. Good luck and have fun trying them out.
Thus the PR-410HLF W/PF-500, lol, guess who won... :O
SPECTOR/Ampeg 1, Marshal guitarist 0!