High power amp reccomendations, airy highs a must

To answer a few questions ... I'm driving PSB Stratus Silver i speakers via Goertz MI2 bi wire speaker cables. Pre-pro is a Reference B&K, front end is a Lexicon RT-20 with 7 nines solid silver interconnects.
I consider my system pretty much neutral to my ears with very few minor sins, if any. Only thing I'd like to see improved is a little air in the highs and a little more taut and controlled bass/mid-bass. This has been well documented to be the hallmark of the Stratus speakers, but changing them is not an option, as I have heard NO speaker that can play as loud, sound as real on drums and stay musical at any level .... at least that I can afford. I'm fairly sure a change to a more resolving power amp with a high level of bass control and airy, extended highs will get me that last little bit. Problem is: My budget maxes out at $2000. Used will probably be a must.
I've also considered replacing the tweeters with a world class tweeter from Scan, but have NO IDEA how it would mate with the rest of my speakers in the cabinets.

Yeah ... a Bryston 4BSST was a HIGHLY looked amp I considered, but they are really too pricey for my budget. Most things I have read called the Bel Canto gear leaning to the warm and musical side, which I already have. Haven't heard McCormack's newer DNA Series though, and Belles looks interesting as well. Thanks for the reccomendations.

Oh yeah ... Here's the funny part: I'm a true audophile who listens mostly to complex, hard rock. Think Tool, Korn, ect .... While most audiophiles will scorn this musical taste, I find systems challenged JUST AS MUCH trying to resolve this music as I find them trying to resolve Classical Symphonies.
Making Dynamics and clarity a must ... but running away from anything sounding cold and etched, as listener fatigue will be almost instant.

OK, I have lots of great reccomendations about bass slam and control, but I am also looking to get an airy and extended treble, and I have never heard a Mac amp that wasn't overly warm.
I also received an email saying I should try Nordost Red Dawn interconnects to tighten the bass and extend the highs ??