I am leaning towards a Yamaha receiver for my HT. There seem to be some models designated as RXV something and some as HTR something. HTR 5660 and XRV 630, for example. What do these two three letters mean? Is there any significance to the two "lines"? Having said that, the RXV630 for less than $250 seems like a real deal. It's almost as if I can just buy that for now, while I get smart, which I suspect will take quite a while yet.