It's already become apparent that the cab is what is needed
Yeah, a bad cab can really screw up your sound.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.