The little Ergos certainly like power. If you can borrow a beefier amp I think you will be pleasantly surprised.
That is contentment indeed. Your 25W may be entirely adequate. I have a variety of amplifiers to play with, and I find the E-IXs definitely respond well to more power. That being said, they play in a slightly bigger room than yours, so that may be the hair-splitting difference when I power them with my 30W amp. The other thing that make the difference is your amp doubles its power into halving impedances, which translates into a truer voltage source, whereas my little class-A amp doesn't.
It's not particular sensitive either at 83dB/w/m below 1kHz. At its rated 60W input power, a single driver would be good for barely 100dB at 1m. That also assumes there isn't huge amount of LF to cause excursion beyond +/- 6.5mm.