@curiousjim - no, you do not need to put a load on them at all. In fact, putting a load on the unused channels will also put a load on the main power supply of the receiver. Just leave them disconnected.
Everyone has their opinions, but I found that the Yamaha line of receivers is the most natural sounding (no pun intended) - when compared to Sony, Onkyo, Integra, Anthem Arcam. Sony is very cold/bright sounding. The rest of the Japanese receivers are typical over-bright and too "solid state" sounding. Anthem is good, but I think it’s still a little too much on the bright side. Marantz is a bit too much on the warm/slow side. Arcam has it’s own sonic signature and many people like it. Arcam is definitely very refined, but to me it just does not sound as realistic as other receivers - mostly due to its Class G amplifier design.
Like phil9624 suggested, I would look at the upper lines if you can afford it. I recently had to buy a receiver for my mom and ended up getting the Yamaha RX-A2070. The two top models are 2070 and 3070. The 3070 was over $500 more and only weighed a couple extra pounds (not a huge difference in transformer size), so I settled on the 2070. Putting in a Furutech 10A fuse and upgrading power cord gave me very excellent results on this receiver.