My tone.

It's already become apparent that the cab is what is needed
As some mentioned, I've tried taking the marshall out of the equation and using the onboard 2x10s and I've cut the bass end a bit more. The tone has improved, a lot more woody (why I like the TB) bottom end nice and tight and clearer highs. Long term I think a tube amp with a fender will be better, but for now the advice has been brilliant and reminded me why I joined Talkbass originally. Thanks all.
Yeah, a bad cab can really screw up your sound.