SET - Limitations from Amp, Speaker Match, Both?

Considering diving into the lower-powered tube world for a second system -- amplifier and tube compliment far from decided at this point, but let's assume the world of the 45 and 2a3 for sake of argument.

I obviously have little listening experience with the low-powered tube amplifier world as well as SETs specifically.

I have read of the enjoyment folks have had.

I have also read of many limitations, some in extension, some in detail, some in dynamics, all from various angles and system configurations.

Let's assume a relatively popular 45 or 2a3 amplifier, exotic parts, but no exotic topology or anything, paired with what would be considered an ideal speaker for it -- no crossover, extremely high sensitivity, and an extremely easy load that matched the amplifier as perfectly as you could come by.

Let's also assume that we're working with a speaker that doesn't go extremely low -- let's say its +/- 3db point is 30hz or 40hz or 50hz..

Eliminating much of the typical issues of system matching, and assuming an ideal loudspeaker, what limitations remain?

With the right matching, is a 2a3 or 45 based amplifier suitable for all musical styles? A thriller of a movie, hard rock, techno, the sound of a chainsaw. These obviously aren't what I'll be listening to, but I'd prefer to choose extremes to truly understand what the end result is...

Are headroom and dynamics simply a function of the amplifier and speaker matching, or do limitations exist with a typical amplifier as well?

Just curious if in an absolutely ideal match of wattage/voltage and transducer, what limitations still exist.
As a fan of the systems you descibe, I think your assumptions are a little off. A low power SET amp coupled to a high efficiency driver in a properly designed cabinet will be about as dynamic and as detailed as you can get. There will be plenty of headroom.

The limitations are at the bottom end. I would describe a speaker that goes down to 30Hz as one that goes pretty darn low, but you are not going to get there with a low power SET unless you have a very large cabinet. I mean VERY large. I supplement my Lammhorns ( with Lowther DX-3 drivers driven by about 2.5 watts of 2A3 power) with an MBL sub. Even if I do say so myself, it is an excellent sounding combo that will play very loudly and cleanly when you ask it to, and sounds wonderful at what I would consider normal listening levels. I have never been happier. Well, there was that cheerleader, but I digress.

Some will say that these systems sound so good because they produce distortions that are pleasing to the ear. Perhaps, but who cares. While chasing the holy grail with very expensive and highly regarded high power amplifiers and multiple driver speakers, I would sit and listen and wonder what I should do next to improve the sound. Now I just sit and listen, tap my foot, and enjoy myself. Isn't that what we are all looking for?
I agree with Herman's statement above that the detail and dynamics are as good as it gets. The lowest octave of bass is the weak point. But everything else is so good, and there is such a small amount of lower octave used in most music, that you really never miss it, unless you are a pipe organ nut. Try to get an amp with good transformers, because that will eliminate the frequency extension problems that some people hear with the cheaper amps that have mediocre transformers in them.

I'd say the Lowther, AER, Reps-1, Fostex, and some other single drivers, like Moth Audio, Loth-X and such, are the way to go with a SET amp. There is a certain synergy between SET amps and single-driver speakers that can make this type of package sound better in some ways than any other amp/speaker combo. For this reason, it is better to go with an efficient single driver speaker, instead of an efficient 2-way.
You need at least 92db efficient and a very stable impedance before trying 2A3s. Anything else and cymbals will sound more like they are made out of plastic than metal. This is a good indicator of serious lack of power. As regards 45s, you need 96bd minimum! Same reason.

I use 300Bs (Air Tight amp) because it literally doubles and triples the number of speakers available. Am I the only one who has noticed the following: In general, the more efficient and easy to drive a speaker is, the more likely it is to sound sterile, "hand-cuppy", and lean? Any ideas out there?
I use a Will Vincent SE 45 with a pair of Altec Santana 1's. Sensitivity 100db at one meter. 15 inch BiFlex woofers - excellent bass impact and drive! All from a mere 1.75 watts! Vintage Altec or JBL is the way to go with low power tube amps!