If you must put tube equipment in the same end of the room as the speakers usually you can put it in the center of the space between the speakers. Just put on some bass heavy music and move about finding the location where the bass response is minimal, usually well away from the back or side walls behind the speakers where the bass is reinforced by the boundries. If you are into TT's the same rational used for locating a turntable can be used for tube equipment.
FWIW, I've never thought that power tubes suffered very much, if at all, from the vibrations created by the speakers, but the small tubes are another issue. I have put large mono tube amps very near speakers (between the speakers) without any issues, but as indicated above I shy away from small tubes that aren't free of microphonics.
