I have a B52 Lg-100A half-stack and I'm trying to figure out whether or not it would make a significant difference in the sound if i upgraded the cab rather then the amp. The amp is definitely powerful enough as I've played with it as a fullstack.
Is the cab the standard one that comes with it?

You could consider trying out a Marshall cab.. remember, it's the cab that actually lets the sound out of the amp. See if you can try out some cabs at your local store, see what suits you.

EDIT: But if you're really unhappy with the tone, it probably is the head, but still you could (maybe) save cash checking out cabs first.
speakers do make a diffenence to sound.
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Quote by CoreysMonster
Meh, I usually just buy them off the local shaman, unless I'm in the wilderness, where I rely on raw meat to raise my HP.