I had a Mk. IV with a Graham 1.5t arm. This table is now in a friend's system. He switches out the arm, most often using an SME 309. The table sounds good with any good quality arm on it.
After a certain cost/quality point, differences between tables can be more a matter of taste/system matching than an absolutes about which is better. I am sure there are tables in the same sonic family as the Mk. IV that are, in absolute terms, superior, but they are going to cost WAY more. I think my Basis Debut vacuum table has the same kind of sound (well dampened and not as "lively" as some other tables), and is superior, but the price difference is VERY substantial. In short, your VPI table is more than good enough so that you are already on the steep part of the slope of the "declining marginal return" curve. I personally think this table is more than good enough to justify use with top quality arms, like the Triplanar, Vector, and the SME IV you already have.
If you have a helpful dealer, easier alternative upgrades to try would be a cartridge change or phonostage change. Both tend to make huge differences, and home trials are more of a possibility.
After a certain cost/quality point, differences between tables can be more a matter of taste/system matching than an absolutes about which is better. I am sure there are tables in the same sonic family as the Mk. IV that are, in absolute terms, superior, but they are going to cost WAY more. I think my Basis Debut vacuum table has the same kind of sound (well dampened and not as "lively" as some other tables), and is superior, but the price difference is VERY substantial. In short, your VPI table is more than good enough so that you are already on the steep part of the slope of the "declining marginal return" curve. I personally think this table is more than good enough to justify use with top quality arms, like the Triplanar, Vector, and the SME IV you already have.
If you have a helpful dealer, easier alternative upgrades to try would be a cartridge change or phonostage change. Both tend to make huge differences, and home trials are more of a possibility.