Which amp to use?

A Harman Kardon 430 receiver. That was easy.

I believe Manley and/or VTL make some high powered triodes. For less money c-j might float your boat. Good luck.

I'd be part of the "some'" that would recommend you may want to consider more sensitive speakers if you are looking for SET magic. 88db just don't do it, and I speak from direct experience (actually I tried 89db with 8 watts in an @ 200sf room with 8 foot ceilings). At low volumes it can be stunning, but for full range at higher volumes it'll leave you wanting and would never hold up to your ARC with the same speakers. The vertical bi-amping solution offered by Marakanetz may be a great solution too, but I have no experience there. My horn speakers are 104db which makes the 8watts from my 300B SETs go a long way, and is VERY satisfying to me. Though I've done no direct comparisons with the 300B push-pull alternatives, I did own an EL34 based pair of push/pull triode amps which were very nice but ultimately would not hold up to my 300B SET in terms of atmosphere and holographic soundstage. Nor would the pentode or the ultralinear amps I've owned. Sure they can sound great and all have their own nice qualities, but I prefer the SET for the refined sense of atmosphere it lends. Were I looking for a fuller range in terms of Push/Pull Triode designs I'd consider the better designs utilizing the 6C33 tubes by BAT, Lamm, or Quicksilver. Any one of which would cost some large coin and are currently out of my price range. Just my two pennies.

Marco

Seems like a situation for bi-amlification.
If you have dual binding posts in your speakers, you should remove built-in crossover and get an electronic one.
Extra amp and extra electronic crossover will certainly rise the cost of system significantly.
As to the full-scale orchestral music not even 110W/ch enough even without speaking of VAC 30/30.
Some may recommend you to take more efficient set-friendly speaker but in reality they're not rated truthfully especially towards the full range.