The music recordings and mixing are also very important. Some albums just don't sound as good as others no matter the speakers.Have you listened to the "Yo-Yo Ma Plays Ennio Morricone" and "Dave Matthews & Tim Reynolds Live at Radio City" albums?
A Klipsch THX Ultra2, Jamo THX Ultra2 or JBL system would work.
But something from Revel Performa-series, KEF R-series, RBH SX-series, and Atlantic Technology would be just fine.
No need to mix the brands. Use one brand for all the speakers. The subs can be different brands like HSU, SVS, Rythmik, etc.
The Denon X4000 is an excellent choice IMO.
For speakers, you might be able to find a nice dealer who could get you a pair of Revel F206 (MSRP $3500) for about $2500. Then get a subwoofer from Rythmik, SVS, HSU, etc.