Suddenly, things are sounding awful...

sounds funny but.... have you made sure that all the contact points have been cleaned on the cables and equipment? Have your actual room changed in it's treatments in some way unlike that which had been before? In the new set up has the placement of the speakers changed in the dimentionality? such as from short wall to long wall? Just some added things to could make a difference for you.

I also think it's the room...

See if you can put things back to the way they were previously. Once you do that, you'll know if it was positioning or if your tastes have actually changed during this time.

I think the system was cold. Reevaluate after a day or two of leaving it on and see.

Lousyreed, Re, "Perhaps thats not right"........

It's not right. The room and speaker positioning in it has a far more dramatic effect on the sound than most folks recognize. Even some of the folks that do, still underestimate it. Life (for us thats audio) should be so simple. :-) Trelja's idea is a good one if you can still do it, at least you will know if you have a piece of equipment that has changed. PS I don't think its the tube - when they age they get dull, lifeless, and noisy. New tubes can be a bit bright for 24 hours or so.

One of the many things that can happen when you rearrange speakers, for example, is in the new position you may well completely change the frequency respone curve in the lower mids and/or bass because of the rooms dimensions. Thin out the lower-mids and the highs will now 'seem bright' even though they may not have changed at all.

It really is amazing how many times I've been told about room acoustics and how many times it has failed to sink in! I'll keep all this in mind and not freak out too much about tubes. Thanks guys.