Can't comment on the value of those Mesa but there is a single recto at the place where we rehearse. Not a bad amp but to my taste, my 6505 eats it alive. YMMV
As for checking the amp. Make sure all the knobs/pots work and that they are not scratchy sounding. The 5150/6505 are well built. Check for heavy/deep bumps on the chassis. This could give you a good idea if the amp has been dropped. Any cosmetics issues too.
As for checking the amp. Make sure all the knobs/pots work and that they are not scratchy sounding. The 5150/6505 are well built. Check for heavy/deep bumps on the chassis. This could give you a good idea if the amp has been dropped. Any cosmetics issues too.