The Yamaha would be my choice. It's a big cut above the RX-V665 in features, build quality, and fit/finish. I also think the Yamaha looks much nicer than the Onkyo TX-SR608. Looks aren't everything though. Performance wise they should be fairly comparable. The Yamaha features preamplifier outputs for all channels, which I won't buy any new receiver that doesn't have it as they can be more than useful at times, they may even be a necessity at some point.
