The DAC has been very refined over the years, it's hard to differentiate between similar cost DACs sometimes even lower cost ones. Speakers, room acoustics, and source material (not the hardware itself, rather the software) will dictate your SQ. Most receivers are transparent, not leaving a mark on the sound (as neutral is possible). If you have 4 ohm speakers, or plan getting them, the amplification will make a difference as well. The amplification only really makes a difference when more power is called for, unless the amplifier you chose is either extraordinarily cheap or defective in some way.
The R-872 and R-972 should both handle 4 ohm loads, it's unlikely they will do as well as the Onkyo however. The Onkyo TX-SR805 and TX-SR875 bench tests are very impressive (both receivers run very hot for receivers due to the amplifier design). If you should chose Onkyo you will need to make sure they are well ventilated or force cooled (by an external powered quiet fan).
Another suggestion would be to look heavily at receivers like the Yamaha RX-V663 (slated for release in April) and pairing it with a solid power amplifier. Another suggestion would be to get on-line and get the Emotiva LMC-2 preamp processor with the XPA-5 power amplifier. The Emotiva XPA-5 is a 200 watts x 5 amplifier and the LMC-2 pre/pro features HDMI 1.3 along with the new Genesis DCDi scaler (which will compete with the higher end scalers available from Anchor Bay Tech 'Yamaha RX-Z11', and the Reon HQV Realta processor 'Integra DTC-9.8').
If you chose the Yamaha RX-V663 + power amplifier or Emotiva XPA-5 (which could be used with the Yamaha RX-V663) + LMC-2 you have the flexibility to power most types of speaker arrays because you will have that power amplifier all the time, even after you upgrade to a better or more current preamp/processor in the future.