Uneven balance

Have those new tubes tested with a tube tester(unless they were already tested/matched to begin with). The transconductance of your tubes for the right and left channels in your preamp and/or amp might indicate a considerable difference or mismatch. If this is the case it might explain the difference in perceived output you hear between the right and left channels. This is not an uncommon occurence.

I agree with Opus88.
Check your bias settings. If there off due to re-tubing, it will cause the ballance to be off.

A quick way to check if it is the tubes, assuming biasing et al is not fast and easy, just switch the speaker cables at the amp (only) and obviously just for testing. If it is the tubes, the opposite speaker will start sounding louder. If not, it sounds like it is a room placement/acoustic issue. Of course, it is assumed that the speakers (cross-overs) are not presenting the issue and that you already checked this.

Thanks for all of your responses. You guys were right on. A simple removal of wall treatments made the new Audio Physic's sing.
Bogeybuster49