daokiYour Yamaha PC2002M only needs 0.77v input for full 240w out!!!!. Most sources today are more than 2v!!! The last thing you need is even more preamp gain as well..
And your Polk Audio RTI A7 are nearly 90db efficient!!!
You need a preamp with little or no gain, otherwise your volume control will be a 8am for very loud already.
For preamps I suggest a very nice low gain preamp that will let you decided on the fly between passive, tube or solid state output flavors. And it has every extra you could need.
The Schiit Freya, at $699 it’s a bargain, and you can send it back.
It has become a huge hit with many, and hated by some that are in competition to it, or love million dollar looks.
http://www.schiit.com/products/freya
Or you should really try this before buying a preamp, "no preamp" for the most transparent/dynamic sound for $0. Your Yamaha has very good Black Beauty Alps input pots (even better than Alps Blue Velvet), you should try your source direct into the poweramp and use these Black Beauty volume pots for controlling your volume.
And if you like it, I'm sure you will, but need more inputs just get an input switch box.
http://www.goldpt.com/sw4.html
Cheers George