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
@kosst,

You completely misread my post. I was speaking of low-volume dynamics. I don’t know how you confused my statement unless you simply read it too fast. This is what I said,

His original post stated that he noticed a lot of "imaging" loss at lower levels. Maybe he was referring to imaging in the true sense of the word, but I’m betting that dynamics is the more appropriate adjective. I’ve never had an issue with low-level imaging, but all mid-efficiency speakers I’ve owned struggled to produce decent dynamics under 70db

Since you mentioned LS50s, I happen to own a pair, and they, like other low efficiency speakers, have weak dynamics at low volumes. It doesn’t matter if one feeds them tube, SS, class A, or AB power, nor does high or low damping factor make a difference. They simply need a certain level of voltage to open up and that means louder volume.

Anyway, the OP subsequently confirmed what I suspected, that he was actually referring to dynamics, not detail or imaging.

What folks here seem to fail to comprehend is that many listeners want the same "jump" factor (mostly regarding bass) at low volume that they get at higher (80db+) volumes. Amp manufacturers began to compensate for this with "loudness" controls once low efficiency speakers became the norm. Then the movement toward minimalism and home theater came about. AVR manufacturers know that most will only use these products for home theater, so inclusion of a loudness control is no longer worthwhile. The boutique minimalists swear that any such control compromises the sound, and/or the BOM for the rest of the amp. That leaves one the option of using separate DSP, an EQ, or high efficiency speakers to attempt to compensate for the loss of low-level dynamics.

Any honest speaker designer will attest that high efficiency speakers produce superior dynamics at low volume. I know you don’t like to read that based on the speakers you own, but it’s the reality.

I own both high and low efficiency speakers. I don’t consider either approach inherently superior. Each approach has strengths and weaknesses.
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Hi Al,
 Thanks for the additional specifications,  I was relying on information from the Polk website. "If"  the tube amplifier has good quality transformers and power supply (PS) I feel the same as atmasphere.  This type of tube amplifier using its 4 ohm tap has a very reasonable chance of success. Atmasphere's recommendation for about 20 db of NFB (or thereabouts) makes sense as this would lower output impedance and conversely increase the DF (Damping factor). 

Meeting this criteria and the need for quality transformers/PS is the challenge for the stated budget for such a tube amplifier. 
Charles 
30 watts was a minimal recommendation to provide moderate/reasonable listening levels. All 30 watt amplifiers aren’t created equally. There is a hierarchy of quality that definitely exists. For example I would be confident that the VAC Renaissance 30/30 amplifier (excellent output transformers and PS) could drive this speaker from its 4 ohm tap and produce beautiful music while doing so. Problem is you won’t find a used one anywhere near 1K dollars. A used Cayin, Line Magnetic or Quicksilver in the 50 watt range push pull class A/B would work pretty well I believe. Interesting thread.
Charles
Moskaudio, am I to understand that you are now considering replacing both the speakers and the amp and going to a 2 channel system? If so I would suggest that you search out the desired speaker first, pair them to your Rotel stereo amp, which seems as no surprise to me to be superior to the Yamaha AVR, while your explore the market for an upgrade in amplification. Finding speakers that are at least moderately easy to drive maximizes ones budget towards amplification.