You have to ask the question whether you really want to mess with tubes in what seems like a combo HT/stereo setup. Also, B&Ws are not the best speakers to use with tube amps in the first place as they require more power to really open up than tubes can usually provide(unless you're ready to plunk down big $$$). Personally I think you'd be better served by trying a warm sounding solid state amp, like Classe or maybe even McCormack, or, better yet, consider replacing the speakers. I'm very familiar with the 602s and although they're an outstanding bargain the tweeters are a little on the hot side, which sounds like what you're hearing. I think you're starting to go down a VERY slippery and expensive slope trying to tame your speakers with electronics--try new speakers first. Given what I said above, I actually question whether this dealer really has your best interest in mind here at all. Best of luck.
Tim
Tim