I use a lot of basses but I do use my Spector which gets me close on its own.I actually love my VT into my 75' SVT. I can leave my SVTs eq flat like usual and make minor adjustments on the pedal. Also have a separate drive on the VT which is nice for when I wanna get my tone really harsh.
I've actually been playing this pedal more then my B7K as of late but I'm keeping the Darkglass for the DI. It's great for live use and recording.
I think a lot of the tones you're seeking come from the bass and the players hands. Both bands you mentioned (Alice In Chains and Pantera) both played Spectors. They definitely have a certain sound to them that I find other basses can't achieve. What kind of bass are you playing?