I use an Emotiva UMC-200 (HC preprocessor, fine for stereo too),a Crown XLS 1500 amplifier (intended for professional use) and Quad 22L loudspeakers..
The most noticeable upgrade was the automated room correction included in the preprocessor. It more or less removes the room acoustics from the equation, as well as the speakers coloration.
IMHO correct speakers, powerful amplifiers (professional audio power amplifier may be considered) and good room correction makes a great combination.
I too use a similar setup with an Emotiva UMC-1, QSC RMX 1450, Mirage Omni 550s and a Pinnacle Baby Boomer. To be quite honest, a few of the decisions were based on emotion, others on what was cheap or what I already had. I love the setup though, it sounds great and gets louder than my room can handle while staying very clean.
Heard several loudspeakers in a local hifi shop and chose the Quad.
For the HC preprocessor there wasn't much choice available at Emotiva price point.
For the amplifier I was leaning toward a Yamaha from the P-S series (http://www.yamahaproaudio.com/global/en/products/poweramps/p...), Crown happened to be more easily available. This one and the Crown have regulated fans. The Yamaha has less distortion and a security cover to lock volume knobs settings..
The most noticeable upgrade was the automated room correction included in the preprocessor. It more or less removes the room acoustics from the equation, as well as the speakers coloration.
IMHO correct speakers, powerful amplifiers (professional audio power amplifier may be considered) and good room correction makes a great combination.