Suggestions for an amp

As the other guys are alluding to, you probably want something more than the Marantz.  The Silver 8s drop to 3.5 Ohms in the midrange, which is not uncommon, but the P8006 puts out 70wpc and only rises to 100wpc into 4 Ohms indicating the power supply is probably not be up to driving your speakers fully.  It only weighs 26 pounds, so these limitations make sense.  By contrast, the Hegel weighs 42 pounds and puts out 150wpc into 8 Ohms and 250 into 4 that your Silver 8s could surely make good use of.  $1600 is a very nice deal on this amp, and you'll thank us once you hear it with your speakers.  

LOL...I'm definitely going to see if I can swing it...

Don't think I mentioned in the beginning...I actually picked these up at a consignment shop beyond reasonably priced. I think people thought the speakers did not work because the links were missing.

They were going to replace my B&W DM640i's that I have had for 25 years. I am guessing if I hooked these up to the Hegel they would take on a new life as well.

I own an Anthem MRX710. I picked it up for $900.00 It is SWEET. It delivers more detail than I had hoped for. Look for one! Good luck Joe

Musical Fidelity M3si will give you more than enough power and a great sounding DAC. If you can swing it go for M5si although you don't need it.

Does the Yamaha sound bad? If you kept it, maybe pick up a used Parasound HCA1200ii - I just saw one on that list site by me for like $500. Then use your Yamaha to run all the surround speakers and the Parasound to run the Monitors. Then you can take the money you save and get an REL subwoofer. The new 12" home theater subs are pretty reasonable...
Just another option, not saying it is the best one.
-Geoff