In my (limited) experience switching between low power class A, 100 watt tubes, high power class d and now higher power class a/b with my Thiel 2.4, power requirements seem to depend a bit on what you want to get out of the Thiels. I found the sound pleasant with all levels of power and definitely preferred the tube sound for things like solo acoustic guitar or small ensemble jazz, and maybe also with minimal house and ambient. However, with both the high power class d and the high power class a/b, the speakers seemed more capable of sorting through things like complex orchestral music. With lower powered amps, it was noticeably harder to distinguish between individual instruments with that kind of music.
Now if I wouldn’t listen to orchestral music often, I might have stuck with the tube amp as this made the speakers more forgiving of bad recordings, and I really enjoyed the warmer sound for pop/folk. These speakers really take on the sonic character of whatever you attach to them in terms of sources and amplification I feel.
I guess budget would be a confounding variable in this little theory though: perhaps a top-of-the-line lower powered amp will produce better results than a not so well made higher powered amp, as the former will probably be able to handle complex music better regardless of power rating.
77jovian, if I were in your position I would go for the speakers, and then see if you feel Iike you are missing something with your current amp. Chances are you might not, depending on sonic preferences and music tastes.