Headroom only comes into play because of louder listening requirements but not at typical listening levels. Off course, this would be offset by room size. For smaller listening rooms, there is no need to feed the Pioneers that much power. They would not sound any different whether amplified through a receiver or seperates like you suggest. For larger rooms, I wonder if the Emotiva would simply over power the Pioneers which in that case would render the combination ineffective.
I beg to differ. Even at below driving amplifiers to their limits, amplifiers can and do perform differently and it does translate to sound differences to. We've run many fun experiments in the past here using a Panasonic Class D receiver and a Marantz linear amp and at low power levels people clearly heard the difference. The Panasonic had poor control of bass and just didn't sound as warm as the Marantz.
I've had similar experiences when reviewing the 8T system with various amplifiers.
If you honestly have convinced yourself that all amps sound the same at modest power levels, then by all means don't waste your money on separates.
For others, separates make a lot of sense. They give you flexibility of changing out the processor as tech changes and more flexibility in using better quality amplification. You often get better preamp stages and DAC's which again translates to better sound. Separates are often easier and less intimidating to setup and use than A/V receivers jammed packed with features.
Most budget receivers these days either don't have preamp outs or they clip with 1Vrms which isn't enough drive signal to reach maximum gain on most power amps.
Seriously it seems lately this forum has become a race to the bottom of recommending only the most inexpensive gear. Most of the critics Diss product recommendations on stuff they actually have NO experience in using.
The Pioneer speakers are actually damn good for the money and as with any good speaker, throwing better amplification at them is NEVER a bad thing.