Wow...how time flies...I had a TX-SR600 when it debuted, now I have the 605 and NOW they're on the 608...
I am a tried-and-true Onkyo afficionado, and I think they do the best receivers especially given the price point. There were some interesting points made in this thread, so let me just throw my two cents in, for what it's worth...
It's true when it's said that 99.9-percent of "600" series owners are not really interested in adding an external amp to the receiver, hence the justification for a lack of preamp outputs. However, it really doesn't make it any less of an "enthusiast"'s selection; I consider myself an avid home theater enthusiast (not QUITE audiophile in many senses of the term) and I simply could not afford anything more expensive that decoded TrueHD and Master Audio at the time than the Onkyo 605. I know this has been cleared up in previous posts between certain members, but I also wanted to add that I don't think these receivers are that "little" or "good enough just for pretty much a bedroom setup" (these weren't exact quotes, but I noticed one member's reference to "nice little bang for the buck receivers")...I am running a 605, with "only" a "mere" "rated" 90 watts per channel, in a decently sized, medium-ish type room and the power seems more than enough, never getting to maximum drive whatsoever. My parents' system is still being driven by an 80 watt per channel 600 in a very large room with 9 foot cathedral ceilings and that surround system SCREAMS. My point is, I don't think all the "criticisms" the 600 series Onkyos get is really warranted; they're not that underpowered for most applications and I really do believe they can power more than just a bedroom system.
That said, let's go back to the preamp debate on this series. It's true that the majority of 600-series owners don't need an external amp, but on the other side of the coin, there's an argument to be made that it's THESE kinds of on-the-lower-side-of-power receivers that could USE or NEED the extra boost from an external amp, so why aren't they equipped with preouts? I understand both sides, but there's probably a **** load of price point politics that Onkyo (and others) consider in these models.
My fantasy would be to use the 605 as a preamp and add a power amp at some point (even though I said the receiver has enough muscle for my current needs, you never know when you would need an amp) through the use of line-level converters or something along those lines, so I can continue using the 605 as a preamp and processor, but I have been told this process is ridiculously "ghetto" in approach, and I should just start over with a new receiver that has preouts. In any case, this information about the new 608 was interesting. I think, though, that the model could benefit from preamp outs, as folks buying 90 watt per channel or so receivers would maybe want more power down the line ("above-average consumers" such as me).