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


Hello. 

 I have some polk LSIM707s that I thorough enjoy.

However, at the moment I'm powering them using a Yamaha aventage 3070 receiver which at 150 watts at 8ohms sounds pretty darn good. 

However, since these are rated at 300 watts at 8 Ohms, I assume I will need some more power. I notice at lower volumes a lot of the imaging and clarity disappears. 

I am looking at buying a 300 watt emotiva Amplifier, or a 500 watt emotiva amplifier.

I'm assuming it would be better to purchase the 500 watt per channel emotiva so the speakers won't suck it dry or stress it. 

Am i wrong in this assumption? 
moskaudio
Post removed 
As for the Quad electrostats. Right now I am listening to my 2805s driven by a 2x140 watt Quad 606-2, at almost full power. The sound is glorious, but to be honest, realistic level would require more power. For a larger listening room like mine Quad's UK engineer recommended their 2x260 watt QSP monoblocks. They are on my wish list. The modern 2805's are far less sensitive than my older ELS 57s.
Too late to correct: QMP monoblocks. The QSP is the modern equivalent of my 2x140 watt 606-2.
@willemj , I think you might be confusing sensitivity with efficiency. They are not the same; the latter is based on power and ignores impedance, the former is based on voltage and impedance thus matters quite a lot!

Now if you are driving a larger room, you will need serious power regardless. If that is the case, you might consider a set of Sound Labs, as they are better at playing the higher sound pressure levels you might need in a larger room.
Many good suggestions here, two that stand out are:

If you increase power and keep the same mass market level of product, you will hear little improvement.  Be sure to go up in quality vs. power, you will hear the difference.

You should audition a good quality tube amplifier.  Tubes have a different sound that many of us prefer.  My preference is for Conrad-Johnson products in both areas, many c-j amps are available on the used market.

Enjoy the search...