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

Dtrandal, I concur with those that suggest that those speakers are the limiting factor. You are only going to get so much bass out of such small drivers. That said, I’ve owned a few Adcom amps, and they really do have great bass with decent detail.

They still make amps, by the way, and instead of buying a decades old used one, you might consider something from their current offering. I’ve had both the 555MS and the 555SE at 200 wpc.

I would suggest the 565SE, at 250 wpc. But, it needs around 2 volts at the input stage to achieve full power. Can your preamp put out 2 volts? By way of comparison, your Outlaw amps achieve full power with only .85 volts, or 850milivolts. So if you are getting really loud before your volume knob is at 10 o’clock, then you probably have close to 2 volts potential anyway. Depending on the volume pot scheme, that is.

Or, if your preamp has XLR outputs, you could buy a couple of Schiit Vidar amps and employ them as monoblocks(they operate as mono's when connected with XLR) for 400 watts per channel. I also have that amp btw, another great option.

I've compared my little Dennis Had Firebottle amp to other tube and SS stuff and have concluded that there's something about a well made single ended tube amp that just sounds musically right, and no push pull amp I've used over the years even comes close, including tube amps. I'm fine being tied to efficient speakers as they also seem to sound better than otherwise, and a lower powered SET or SEP matched with the right efficient speakers will work to make music play loud and clear with no transistor glare or artifice...I do use a few hundred SS watts for my subs though...matches perfectly.

my audiolab 6000A preamp can output a maximum of 2.3V. I will take a look at the Adcom 565SE. Sadly, it does not have a true balanced XLR output, but that is certainly a feature i’m considering for down the road.

93db speakers are not that efficient. They will take some power to drive. I use Altec speakers that are around 99db and drive them with Mac MC40 monoblock tube amps. At normal listening levels (loud) I'm not using even a watt of power. If I crank them up till I start to hear some distortion (clipping) they are way to loud.
When I got into this hobby I was always chasing bigger amps, more power, had in-efficient speakers and thought that was the only answer. After a buddy showed me what a few watts on some Klipsch horn speakers could do I had to re-evaluate my thinking.
I also wonder on an amp that is designed for say 300watts, just how good is that first watt of power. Are the solid state devices really that linear at levels just a tiny fraction of their rated power? At 1 watt it would be running at 1/300 of it's rating and on softer passages less that 1/3000 of it's rating. Tubes seem pretty immune to that sort of thing, at least my Mac's are.

Billwojo

For high efficiency speakers, amps ar a big deal. IMO, an amps output "gain" is key. Or should I say, the combination of your pre and amp's output gain. If really high (especially with tubes), you will be more prone to hear hiss, noise, etc with high efficient speakers.