Just a bit of sharing. My personal opinion is you should upgrade the source first. The sony SCD-1 seems to be the weakest link in the system. I am not sure if you mainly listen to redbook CD or SACD. If it's the former, I strongly suggest upgrade the CD source first. It has a profound effect of the overall sound. The reason is I have previously owned the SCD-1 and it's hugely disappointing for playing regular CDs.
Personally, I am using CJ 16 preamp, CJ premier 350 power. Previously, I have also owned CJ premier 12 monoblock, ARC LS25 and Ref 2 Mk 2 preamp. I think the choice between CJ and ARC shouldn't be difficult at all since they have a distinct taste in their own good. In my city(HongKong), the ACT2 cost almost double the price of Ref3!