For efficient speakers, how much difference does an amp really make?

I have ascend sierra RAAL tower speakers with 90-93db efficiency and 300W continuous power handling. I’m powering them with dual outlaw M2200 monoblock class AB/G amps rated at 200W into 8 ohms. It sounds good...but i can’t help but wondering if a different amp would provide greater clarity and low-end grunt.

I have been curious about an older adcom amp like the GFA-555 II or perhaps a parasound halo amp like the A23. 

To those who have had multiple amps in your setup, did you find significant sonic differences between amps, or is a subtle thing? I don’t want to start collecting amps, but I don’t want to deny myself the chance to improve my system further. Thoughts?
I like overpowering my speakers always because headroom is a good thing to have when it comes to the sound on the bottom which is extremely difficult to do when you are trying to make the bass notes sound correct I myself am a bass player so I am very critical about that there’s lots of choices
if you have a good dealer that will let you take things home like I do at gig Harbor audio in Gig Harbor Washington they let you try out anything they have on the floor you can bring home I’ve tried lots of amplifiers and I’ve probably owned at least 200 different systems in my life so far I have about six different places where I live and my business it’s a never ending hobby and it is the hobby that will keep me Engaged for the rest of my life
" My system is very happy at low to medium volume levels. The sound is open and clear and produced seemingly without effort. It ramps up nicely until you get to a place where things start to change. The open sound starts to close up a bit and there is a strident tone that creeps in as the volume gets to what i would call “loud”. We’re not talking Wembley Stadium loud, or vibrate the windows loud, but the kind of volume you’d want for a favorite song when you really want to enjoy it.

Maybe the speakers are just tapping out, but i doubt it. i suspect that the slim, cool running M2200’s are simply running out of puff. Whether that means amps or watts...I have no idea, but I suspect these speakers have more to give.

I think it’s pretty clear that more watts are not always better watts...but i’m curious...what is the secret sauce that makes an amp with less wattage capable of driving a system with more authority and gusto than one with higher wattage?

And the big question....short of buying a dozen different amps and auditioning them on your own system at home, how can one even begin to make intelligent guesses about what to try next? "
   I run speakers that are normally at least 104db efficient. The excursion of the woofer for instance is minimal. Efficient speakers mean more DB with FAR less cone movement which results in less distortion. I also use bigger than normal cabinets and horns because the best effortless sound does not come from small speakers. Things that sound good at low to moderate levels will sound bad at higher levels often because you have pushed beyond capable working limits of those small boxes and drivers. Yes you got more volume but the quality of it goes down.
  I run per channel a single 15" woofer inside a big horn and have a large horn for mid to HF using a two inch horn driver and yes it is a two way system. With Crown amps like an XLI800 at 200 watts per channel 8 ohms I can turn the volume up half way on the amps and then about a half of the way up on my PC which I use as a music server and can easily measure about 95db sustained and peaks up to 105db depending on the music from 10' away. I have no doubt I could sail right past 113db with no problem but I am not interested in doing so.
  If your cables and connects (and no I don't mean fancy ones but ones that make good solid connections and normally 12g which is overkill) are up to snuff, as I try to keep mine, a system like this is dead silent on idle and then goes to live performance levels and does not strain to do either. There is headroom to spare and even at low volumes 0f 75 to 80 db it sounds better than speakers that are not as efficient or too small for the job.
  You can also drive speakers hard enough that even if they were really good sounding in your room at low levels above a certain sound level your sound begins to break up and then that becomes audible.

  Bad music files can sound OK at lower levels but when you push your speakers hard those bad files sound even worse. Over time I have given up on some songs I really like because of the poor mastering which ruined it.
  I suspect from your description of your system and problems you have a number of things going on.
  Last but not least is this. Why guess when you can download a free program called "REW" and load it on your laptop, buy a calibrated mike such as a "UMike" and a mike boom and measure what effect each thing has including the system response to your room itself. Finding out where the worst frequency problems occur can often be tamed with a simple stand alone EQ but you could spend eternity trying to just fiddle and get the best results. Yeah it is a pain to learn to use on your own so find someone to help you nearby who can stop in to help you. Then you no longer have to throw more money and gear at an ever growing pile of stuff that still never satisfies you. You analyze what is going on and eliminate your problems one by one.  
I have a 30 year old pair of Klipsch Forte speakers.  They are 98 db sensitive so never thought I needed more than a couple of watts.  Then I bought an old Altec Lansing Pro amp and modded and refurbished it.  200 watts per channel.  Wow what a difference watts make.  Now I don't just hear it, I can feel it.  
Hey dtrandal

The amp can make a huge difference. At 90-93db efficiency your speakers are very efficient and will work with a lot of amps. If you prefer solid state (I don’t know your budget) I would listen to the Pass Labs little 30 wpc pure class A model XA30.8 which is balanced. If you’re ok with single ended his pure class A model XA25, both sound great. I own the XA30.8 and my speakers are 83 dB! It drives them effortlessly all day long and always remained so musical. There’s also a lot of great tube amps out there as well. Any good quality 50 watt tube amp would be all you would ever need. Good luck.

@scothurwitz, what do you mean “Pass Labs little xa30.8”?  That sucker weighs 93 lbs!  But I do agree, it’s a great amp.