If you're mounting the speaker from the ceiling though, upside down or right side up probably wont make much difference in right ness. You're going to be pretty far off axis unless you tilt the speaker, and then you will be targeting a certain area of the floor anyway. Some speakers are...
Speakers are designed for a certain orientation. The baffles, the layout, and the cross over networks are designed together. If you turn it upside down or on it's side, it will change how it sounds, and if you mount it from the ceiling, you'll also have issues with off axis response. But then...
Could be a couple things: 1) bad inter connect * try a different interconnect and see if it's gone or sounds different 2) ground loop hum * Do a search on how to balance the grounds between components 3) bad shielding somewhere in the electronics * Turn off anything else electronic...
I think it depends on how far you have to go, and which speaker you're driving, and how good your hearing is. The mains and center (in HT) are where most of the sound comes from, so skimping a little on the rears isnt so bad, cuz most of what you'll hear in HT is effects, and occasion voices...
1) the tweeter is not a tweeter you can get anywhere. It is very similar to the vifa xt 25, but it's made a little different to spec's that polk requested. 2) I have the 9's/lsi 5.1 driven off an onkyo tx-sr600, and it drives it fine in my smaller room. My old sony without discreet amps got...