Once did a comprehensive AB comparison between a then flagship Yamaha DSP-A1 and Denon AVR5600, back in the day. The speakers I used to compare were little bookshelf B&W DM601's and also full range Mirage M5i tower speakers, as driven by the two afore mentioned AV receivers. I did movie and movie demo's with the speakers, and compared. Then, we switched in a separates Denon DA-8200 power amp for stereo 2 channel music duties. IT WASN'T EVEN A FAIR FIGHT! The performance of either the Denon or Yamaha's could not compete with the power and refinement of the better amplifier, regardless of the configuration (small vs large setting cross, etc) we ran!
What I learned? The amp's in these AV receivers leaves quite a bit on the table, and are not so special.
DO look to get quality amplification in the system, regardless.