I use an IPS-1 with my RX-V1800, which is a very similar receiver, but I don't think I ever ran my current setup off just the receiver, but if I did I don't recall how it sounded, but I'm sure it sounded just fine as the upper end yamaha receivers have good amps built into them. However with the IPS-1 I don't think I will ever run out of headroom, and the amp runs extremely cool since it's a class H design, which is very efficient.
