Those old CV's aren't the best in the world for HT or accuracy, but they're awesome gaming and party speakers. Just the thing you want when you want to crank some AC/DC or something.
I just acquired the 608 (refurb from Accessories4Less for about $300). I'm very happy with it. Functions well, plenty of inputs and outputs, full graphical OSD, upconversion, the works. The 709 has the upgraded version of Audyssey, which is awesome, and adds networking, superior upscaling, and a few other less important things. The most important things for a receiver are just to make sure it has the features you want and sufficient amplification. The 709 is enough for the vast majority of people.