Need some Amp help - a little new to properly powering speakers

Don't waste your money! Going from 150 watts to 300 will only give an increase of a mere 3db more SPL. And that is at the rated limit of the LSIM707's! If you want more clarity at lower volume you need two things: a better speaker and a better amp.I suggest a pair of Quad Electrostatics with Quad amplification! Buying either Emotiva amp is a waste of money! And will not give you the desired clarity. Your Polks and the Yamaha receiver are the limiting factor - typical mid-fi gear! 

@moskaudio You are wading into a subject that will reveal different opinions fairly quickly. I try to get as much quality wattage as I can into my speakers without endangering either them or my hearing. My reasoning is akin, I think, to what you are expressing. For example, my speakers recommended amplifier power is up to 350W (8 ohms). I drive them with monoblocks rated at 430W (8 ohms). I have heard the speakers with an integrated amplifier (by the same amp manufacturer that makes the monoblocks) rated at 1500W per channel and they sounded great, although not as good as how they sound with the monoblocks, IMO. I would describe the effect as the amplifier seeming to have more reserve to allow dynamic recordings to sound abundant while maintaining excellent attendant speed. Of course, you don't want to crank the volume past a certain point or you will be buying new speakers. In sum, I think I'm practicing your assumption and I find it satisfying. And FWIW there is nothing wrong with your gear. It is your ears that hear it and if you enjoy the sound being produced that should always be what matters most.  

I can see that. I figured a fairly expensive flag receiver would produce decent quality power but I guess I should try hooking these up to a 100watt per channel rotel amp I have and see how it sounds.