I concur with your findings on the preamp. The difference between a decent preamp (Classe in your case) and a good preamp (ARC in your case) is so much. If I were you I would get the new preamp, let it settle in the system for a few months and let the ears acclimate to the new sound. After that I would re-evaludate the system. You may want to continue upgrading the preamp at that point, or you may want to get a different amp. But changing more than one component at a time usually results in suboptimal result.
Upgrade amp or speakers?
I have Martin Logan Aerius i speakers, Classe Cp35 pre, Classe CA100 amp and Meridian 588 CD. I am looking to upgrade the pre/amp but don't want to spin my wheels ($$$) if the speakers are not worth the upgrade. the pre/amps I am looking at are the Pass x250.5, BAT vk-250 or ARC SD135. I tried tube ARC VS110 and loved the sound but it was a little too soft and moved music passages to the back. BTW, the speakers still sound great but am I over spending on the pre/amps? Thanks