Some site says it is 89dB, but I think 87dB is correct.
I run it with Plinius SA102 class A 125WPC
Power wise, I would suggest at least 100WPC, preferably a high quality 200WPC amp will do justice. On my setup, I could directly compare Gershman with Harbeth Compact 7ES-7 and Tyler Linbrook Signature Systems. Gershman costs over two times, and it clearly sounds better than those. I like its small size and light (?) weight.