My humble dos pence,
#1 biamp as woodsyi says. Seriously, it will make a significant difference in the performance of the SET amp to not have to drive the bass woofer. Damping factor which is needed for woofers is not the strength of SET amps. Here you can really make your money go a lot further if you use a beefy SS amp on the woofer, then a more attainable medium powered SET amp can be used to best results.
#2 it is easier to make a good quality lower powered SET amp then a higher powered one. Price, complexity both go up exponentially with power. Also 20w SET amp typically have extreme voltages (900+) in the power supply making them a risk if you have small children/pets.
#3 IMO, there is no rocket science to SET amps. The best designs are typically simplistic, the technology having been around since the '30s. Often times the hobbiest built amp that they sell, as a hobby. This is probably the best price/perf, not having to pay for overhead business costs, dealer markups, etc.
Names of such hobbiest don't come to mind off hand, but I've seen many of their offerings on A'gon. Their designs look sound and unlike many marketeer's offerings, there is transparency to their designs, so any technician can work on the amps. Most often the designs are point to point which make maintenance easier as well as less needed.
Bottlehead is also a good value proposition. Their designs are very well thought out. You aren't paying extravagant markups for fancy ads in hi-fi rags and distribution channels. They use great iron (Magnequest), which is the biggest component to performance in a SET amp.