Help understanding adding amp to reciever

I have a Onkyo TX-NR808 135watts I recently bought a pr of B&W CM8's and I am contemplating adding a 200watt 2 channel amp to power the cm8's for listen to music and ht. I read my manual but it is not very clear on how it will all work together. It says I can add an amp and to go into the receivers menu and select none for channel(s) I don't want to output to. So if I only select none for the fronts and use the front L&R preamp outputs to the amp & connect the speaker wires from the amp to the fronts, then if I'm correct the receiver will power all speakers except the fronts & the amp will power the fronts. But will the receiver volume still control the output to the amp so that the volume to the fronts will be the same as the rest powered by the receiver? Please feel free to straighten out my thought process if I am not on the right track. Thanks for your help. Bacher2741
Correct and yes. You will be using your Onkyo as a preamp only for the front main channels. You should still be able to level match all your speakers (where you listen to white noise sent to each speaker to set the proper volume.) It should be a very seamless transition and you should have no problems.