Why don't all phono preamps include a rumble filter?

Nakamichi also used to make an inline filter that I believe was down around 10 that worked very well, with that said with a table such as yours there should be no need and only take away from it all.

I was Just thinking, as you and I are kind of in the same situation, one of being shoe horned into a given set up in a less than favorable room, you might want to try a Symposium ISO platform between your table and shelf in your wall rack. 

There is no reason to think about changing tables, I too have had three VPI tables never having a rumble issue with any of them, all supported by a lead balloon turntable stand so I started out with a good set up from the ongo. Symposium makes an insert to replace the rubber grommets that vpI uses in their feet that really work wonders for around $200.00. You should be able to get that rumble thing under control with very little effort.

I believe that in the truest sense they want there product to shine in its best light, kind of forcing us into addressing any issues and not making any compromises. Just sayin.