In that range i would have picked up Dali Zensor 3 over KEF Q300. Have heard both paired up with Yamaha.
As you know Yamaha is always considers on the brighter side, KEF Q300 came out too much on the brighter side, however Dali Zensor 3 was much balanced & sound warm too. Can't really comment on paired up with Pioneer AVR bcoz never had option to audition them. Hoz the sound signature of Pioneer AVR when compared with Yamaha or Marantz, its closer to which one?
Cheers,
Binu AP
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LG 42" Plasma | Marantz PM6005 | AJ FS52 | Velodyne Impact 10 | Panasonic dmp bdt220