Hi Bruno, I just bought the M80, QS8, and VP150 setup, and while I haven't received them yet, I was lucky enough to audition them beforehand. I think these speakers have a great soundstage and are definately solid on highs, mids, and lows.
When I was receiver hunting, and it was between the Pioneer 92TXH and the Denon 3808CI, I was listening through some large Klipsch tower speakers (can't remember the model #) at Best Buy. I do have to say that they sounded better than the Def Tech setup they had there surprisingly. But after listening to the Axioms, they definately appealed more to my ears.
By the way, if you're looking for a $700 sub, you may want to check out the MFW-15 woofer on av123's site. It's gotten great reviews. I'll be setting mine up soon, so I'll be sure include my opinion about it along with my M80 review. Just a warning though, it took me over 2 months to get it due to backorder from such high demand.
As far as receivers, I know that Yamaha has the v663 for around $600.
