New amp for B&W 803s - Classe or Mac or ???

There's only one way you can fix your problem. And that is to get rid of your 803's. I'm not guessing on this. I know from experience. There's just no fixing that aluminium tweeter. If you try to find components that will be used as an EQ, plan on spending a lot of $. You'll still have the same problem with you are done.

I didn't mean to be too direct and to the point, but if you haven't guessed, B&W is somewhat of a sore spot with me. I could barely stay seated while reading your post.

I tried everything with those speakers. The upside is, I leaned more about audio trying to get those speakers right than any other experience I've ever had. It was just extremely costly and frustrating. You can try things with the room but honestly, I don't think that will do any good. High frequencies are very directional and what comes out of that tweeter takes a direct path to your ear. (I understand that some of it gets reflected but in your case, thats not the problem.)

If you want to keep your speakers the only thing you can try to do is change the sound of what is coming out of your tweeters. I can recommend 2 products that I think will help. Understand, though, that I consider these to be "band aid" fixes. What I mean by that is you would be using these components to fix something else in your system. Personally, I really don't like doing things like that. I feel that an audio component should be able to stand on its own; without any help.

The first component I think will help is a Jeff Rowland 112 (Or Model 10 or 12's). They're all part of the same line. No other amp I've ever heard handles high frequencies quite like the 112. At first you think its rolled off but the more you listen to it, you realize that all of the information is there, it just gets timbre correct. Things sound like what they're supposed to. Anyway, thats the best way that I can explain it. The amp has its flaws, but it should work wonders on your B&W.

The other component I would look at is a pair of Synergistic Research Signature 10 speaker cables. Normally, I hate to recommend cables to fix issues. This is an exception. Its a biwire cable that uses different materials for the high and low frequencies. Whatever they put in the HF portion of that cable, is exactly what you need for your B&W's. The best way to explain how it sounds is to compare it to the Rowland I just mentioned. It has a very similiar effect. I'm pretty sure the cable is no longer in production so you would have to find it used. If you can't find one, I would call Synergistic and see what would match up to the Sig 10's in their current line. Tell them you want whatever they used for the HF's in the 10's.

Anyway, I hope this info helps. That said, I still think you should treat yourself to a new pair of speakers. If you keep thinking about your problems with the B&W's, I'm pretty sure that you will be able to talk yourself into getting new ones.