I swear by Modded Marshall cabs:
Get a cheap 1960 JCM cab, rip out the backpanel (particle board!

) and stereo/mono switch (do we ever use it? I bet 9 out of 10 guitarist don't).
Get a nice birch multi-ply cut to size, take off the old tolex from the old backpanel or get some new and install a good jack (I recommend Neutik or something similar), replace the thin ****ty wires on the inside with good isolated speaker wires and solder them to the speakers and jack.
Then glue in some isolation foam (I just used the grey type that is shaped like egg cardboard) on the backpanel (yeah that means on the INSIDE!) and on the sides, bottom and top(not the front). Screw the new backpanel back in and you're set.
You'll get more clarity, bottom end and note definition after this mod.
Resources consumed: a couple of hours, a few beers, $50 on wires, jack, glue, foam and wood... All in all you won't get past $500 for a good cab that says Marshall and sounds good to modern standards.
I'm still on the lookout for 2 more V30's so I can change out the speakers for all V30's.