Hello Mdrew,
Hope you are well. I did not answer all of your questions, let me continue. The STF-3 has a lighter weight cabinet and less power than the VTF-3, I would not consider the STF-3 in your situation.
I am still thinking a cylinder upstairs is the way to go with your setup. They give you the most for the least amount of money, and are much lighter to move around. When you stick one of these in a corner of a room they are jet black and most people won't even notice it, you could even get a plant to hide it behind, if you decide on the downstairs placement.
Another benefit of the cylinder sub is that it is lighter weight, for less shipping cost than the box subs. A cylinder resists cabinet flexture naturally, so does not need all the bracing of a box sub.
As far as noise using speaker cable output to the sub, it all depends on how clean the amplification from the receiver is, and then the amplification from the sub. This double amplification will amplify any distortion from the first amp, which is relatively low for the H/K 7200.
If you are running 30+ feet, I would run 10 or 12 gauge wire, if you go the speaker wire route.
Hehe, I know it is out of budget but have you looked at the wooden SVS Box subs, the SVS PB1-Plus and the PB2-Ultra? Beautiful wood finishes, and expensive to boot.
I hope I covered everything this time.
Later,
TonyM
