The only electrostatic's I've ever heard are the O2's. I started out with the 717, running with balanced connections out of a DV-50. I listened to them this way for months and liked them alot with a couple of exceptions. They would play clean and effortless at a fairly loud level, just slightly louder and they would instantly and obviously distort. Just back off a bit and everything was OK.
Curiosity got the better of me and I purchased a Black Gated Blue Hawaii and Telefunken EL34 tubes (I have been listening to this combo for over a year). Much more power, no distortion at high listening levels, bass is ultra deep, tight, controlled, textured (moreso than any other phone I've heard). The high end, especially cymbals sound very realistic and metallic without being splashy. The Blue Hawaii has a much more organic sound than the 717. The 717 sounds more like a great stereo where the BH is more like real instruments in your listening room.
The curiosity thing came up again and I realised the only tubes I'd ever listened to with the BH were the Tele's. I was having trouble believing that the only tubes that would sound great in the BH were these ultra expensive NOS tubes so I tried a set of the reissued Russian Mullards for three months. They sound good but lack in several areas to the Tele's. Primarily the bass although deep was much less controlled, even fuzzy by comparison. The high end on the russian tubes was splashy by comparison.
I had the BH/Tele combo + 717 for direct comparison for several months before I sold the 717. I had not heard one instance on any material where the 717 was preferred over the BH/Tele combo. I still think the 717 is a fine amp at it's commonly discounted price.
Even after all this rambling it boils down to system synergy and the sonic qualities you value most.