Well, I'd agree that for audio quality and prowess, Onkyo is the way to go at most price points. They just seem to have more serious amplifier stages. I just bought and installed an Onkyo TX-NR676 for my mom at $459.99 and am quite surprised and pleased with the audio for that price. My Onkyo TX-NR809 has awesome sound and has never had the dreaded HDMI issue. Now, that said, I think that deal on the Denon X4300 seems too good to pass up. I also have a Denon X5200 and the audio is about as good as the Onkyo 809.
FAMILY ROOM--Legacy Signature II tower speakers(Front L/R), PSB Image 5T tower speakers(Surrounds), Denon AVR-X5200W, Krell FPB 400cx, AR ES-1 turntable w/ Audioquest 404-B cartridge, Oppo UDP-203 UHD Blu-ray Player, RCA HD-DVD player, Samsung HL67A 750A TV
MASTER BEDROOM--Dynaudio Audience 82 tower speakers, Outlaw LFM-1 sub, Yamaha RX-V1800 receiver, Sherbourn 5/1500A 5-channel amp, Oppo BDP-83 Universal Disc Player, Panasonic 60-ST60 plasma TV.