ARC Pre + which SS amp?

I second DNA-500.
However, one note of caution, with the 500, the input impedance of this amp is rather low at 10kohms, so careful matching with a tube preamp is a must. You can't have too high of a gain or you won't be able to finely adjust the volume.

Similar experience as MdConnelly. I have an ARC LS-25 Mk I with GNSC Ref mods, using 4 Amperex 7308 white labels). Switched from a Levinson 333, which I had for 8 years, to a Pass X350.5 about 6 months ago, and my jaw just dropped to the floor. Speakers are Thiel 3.6

FrankC

An ARC 300.2 should be a perfect match. I have an LS15 with the 100.2 and they work great together. I have not heard the 150 and 300 versions of this amp, but if they are anywhere near the 100.2, they are definitely worth checking out.

Audphile1, I have a 700cx with Chario Academy 3 juniors and a Velodyne DD-15 sub.

With my Audio Research LS3, LS25, and Reference-3 I have found that the Plinius SA-50, SA-100, SB-300 (for sale) and SA-Reference sound wonderful!