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

Efficiency and easy load are not the same.  
Efficiency means things get louder faster. 
An easy load means all frequencies get handled similarly and lesser difference to be expected  from amp to amp other than how loud things go. 

Yes a good powered sub or two set up well is a very effective way to address power needs. Power needs for flat extended bass increases exponentially as  frequency decreases which is why most good subs these days deliver 100s of watts often using Class D amplification. Plus use of a crossover that relieves the bass load on the mains usually results in better performance from those as well because now your main amp has to not work as hard as before trying to do it all. Best thing since Swiss cheese......

High efficiency speakers done well is a good thing but good quality full range ones are big bulky and thereby relatively expensive and generally require a lot of room to breathe.  Not for everyone. 
No single approach can do it all best.  Hence the variety. 
Also, these days, high efficiency Class D amps are a game changer delivering more often for less and in a smaller easy to handle package that is practical for many.  

Not all amps of a similar power rating are created equal in terms of ability to drive any speaker well.

Usually amps with ability to deliver more current will perform better with more challenging speaker loads regardless of efficiency rating, which are common these days.

The indicators of an amp like that is ability to double current delivery into 4 then maybe even 2 ohms and usually have higher associated Damping factor, more like 50 or higher rather than lower.  Some amps, the ones I tend to like most,  may include explicit current delivery capability specs.


Used to be these amps were also big heavy and expensive if Class A or even A/b but these days not necessarily the case. Some very efficient Class D amps with better power supply circuitry can deliver a lot of watts and current when needed out of a smaller lighter box. The efficiency of the amp essentially helps compensate for the inefficiency of most speakers out there these days.

Both BEl Canto Class D amps I use are good examples. Look up teh specifications of teh Bel Canto ref1000m amp for example.

Another significant factor has to do with output impedance of pre-amp used. Not an issue with most SS pre-amps however tube-preamps have higher output impedance which means a SS amp it mates to should also. 60-100kohm or so input impedance is what to look for. Some amps are designed this way to work well with tube pre-amps, some are not. Good impedance matching from pre-amp to amp minimizes distortion and general results in better clarity and definition top to bottom.

Regarding Ascend Sierra speakers specifically, I am not familiar with those but the specs I see on the company website for these models in general seem to suggest moderately more efficient than many at best and that they tend to go for somewhat extended bass for their size which almost always means a few extra good quality high current watts could only help since they have to work harder to deliver flat extended bass from a smaller package. A 300 watt continuous power rating is a good indicator that the speakers should be able to handle pretty much as much power as you could ever practically throw at them.

It’s true that listening at too high an SPL continuously beyond ~ the mid 80s causes hearing loss, so if one is armed and dangerous with an amp/speaker combo truly capable of delivering clean, dynamic peaks in the 90s or greater like one might hear at a live concert, be careful. There is only so much of that really good stuff the human ears can handle.

Soft clipping lower power tube amps are a good compromise from that perspective. Your ears are safe and as teh soft clipping kicks in rolling of the dynamic peaks, you will probably hear more of all the rest that is in the recording. That’s still a lot of good music.

Hate to make soft clipping amps sound similar to modern loudness wars recordings but the end result can be very similar.

Disclaimer: I like a lot of modern loudness wars CDs with good material done well otherwise, but only on a  good suitable powered setup capable of delivering the goods.

Years ago I worked in a TechHifi where we live demoed and sold most every line of receiver and amp from 15 w/ch to 200 or so.

The bigger model in every line always sounded best. Nobody ever chose fewer watts after listening because it sounded better.

Watts do matter if you want top notch dynamic peaks. That is basic physics.

A 50 watt tube or Class D amp may seem to deliver more per watt but that is mainly due to the fact that these amps soft clip which makes clipping more digestible to the ear by rounding off the peaks smoothly.

For best performance always best to be sure to avoid clipping, especially hard clipping like most amps but also soft.

How much exactly is needed is very speaker dependent.

My personal experience has been most any speaker benefits from more watts where the amp does not have to ever break a sweat to drive them.

I use 500. W/ch Bel Canto Class D. This will drive almost any speaker to lifelike volume effortlessly without ever getting warm.

I also have 60 watt Bel Canto Class D amp. This is lovely within its SPL limits with most speakers like a good tube amp but more limited in regards to ultimate dynamics and SPL.

If an amp does not clip, chances are it will sound good. What sounds best from there is much more subjective and harder to predict.