I know this is an older post, but would also like to comment. I use an older Plinius 8200 on Obelisk 2's, and this is a fantastic match for them. I can only think that the 9200 would work fantastic with Arc's as they are even easier to drive than the Obelisk, which can be a bit current hungry.
I think the older Plinius amplifiers are a very good bargain these days as they can be bought fairly reasonably and definately have power/current drive, yet retain a very good balance of finesse and detail.
Plinius and Shahinian, they play togetehr very well indeed. Tim