Gershman Grande Avant Garde

You could call the company (talked to them yesterday about something else and they are very nice), or there are reviews on youtube by David and Jay (both from about a year ago).  Listed as 89dB sensitivity but my hunch is you'll be best off with higher power better amp.

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. 

ihcho, sorry to be redundant but do you think a Luxman 507ux will be sufficient?

I don't have a direct experience with Luxman integrated amp, so I cannot say for sure, but from the spec, it will work fine.

Luxman's output is 110WPC on 8 ohm and Gershman is 6 ohm, so Luxman will pump a bit more power (150WPC?) to Gershman. 

However, if you have not purchased the Luxman yet, if I were you, I would go for an amp with more power, like 200WPC on 8 ohm.