Pro-ject tubebox ii : muffled sound


I found a Tubebox ii at a thrift store for a price that I could not refuse.

The sound is muffled, like it is so warm it is in the next room. It still has the original tubes -- is this something that a new set of tubes will likely fix up, or do I need to take it in?

To that end, it calls for 12AX7A tubes, and I'd love any input on choosing replacements (I'm new o tubes) -- the price range and lack of adequate descriptions for tubes is befuddling, but I assume the differences are significant. I can spend anywhere $20 to $2500... hmm.. it'd be nice if the $20 pair worked..

I've been using my McIntosh MA6500's built in phono stage for about a year, and have been happy enough with that.
difficultlistening
The sound is muffled, like it is so warm it is in the next room
Could you explain this a little better please? I'm having a hard time figuring out just what you mean.
I'll try.. At first, I noticed the sound was quieter than my standard (internal SS phonostage) setup, so I turned up the volume, at which time I noticed the warmth of the sound -- highs and lows cut, mids emphasized -- this was all in a few seconds. Once vocals came on it was clear that the sound was not right -- like it was in the next room, muffled, weak sound, loss of detail-- in short: bad.
Okay, I think I catch what you mean now. I've never heard the term "warm" used in that context.