Really, Onkyo makes okay boxed sets and considering most are shit, that’s something to brag about. Onkyo is more known for making damn fine HT receivers and the like, Onkyo making a boxed set is like when Klipsch steps down and makes PC speakers, when they specialize in quality (though horn driven) speakers.
The SR800 is the one to get but 7.1 really isn’t the most useful thing ever and its more spendy. Onkyo I’d call the measuring block for small boxed sets. When I played with a SR800 I recall thinking they were about on par with the Promedia Ultras were but without as much growl.
Onkyo just makes much better stuff than the PC speaker makers, save Klipsch. The bonus of the Onkyos is they’re a little more versatile, and if you ever buy a full fledged Receiver, you can just unplug the speakers from the receiver it comes with and stick them on your new receiver. That way you can upgrade as you go. Plus the receiver it comes with has 3 SPDIF inputs, two Optical, one Coax which means you could have your Mac, 360 and perhaps a PS2 connected all at once. Its the smartest thing to do. Most of the PC speaker makes have back pedaled away from 5.1 sets as its hard to compete at the same price range with something like this.