What is the next Phono Pre-Amp for me?

I've never heard your ARC, but have fairly recently had in two systems of my own a Vendetta ???, an Aragon 47K, a Welborne Labs Reveille, an AHT DM-P, and, last but not least, a Pentagon PS-3. I can't fairly compare the Pentagon with the AHT, since I built stepped attenuators into the AHT (literally built both into a new chassis), but compared to all the rest, the Pentagon wins hands down. There were two for sale on Audiogon the last time I looked. It's one to consider, IMHO.

i have the herron, and had considered the groove. while i have not heard the groove, it's rep is very respectable. i have enjoyed the herron tremendously. it is in a tubed system, and seems to have great synergy with the rest of the stuff. the groove and herron are both totaly lacking of contols (you must order specific boxes for different loads), which i appreciate, minimum interference with the signal. good luck and enjoy it.

An Aesthetix IO would be a very nice phono preamp to have.

It looks to me your system is well matched. What aspect of the sound do you want to improve? If you really want to "upgrade" and if you like the ARC sound, you might want to consider their Reference Phono and Reference II preamp. But they are very costly and I don't know how well they match the rest of your system. You might end up upgrading everything.

What's the rest of your system? Are you sure the ph3se is the weak link? Only a handful will best that one. Some to consider (in addition to yours & your choices) is the BAT VKp10 and VKP10SE, the ARC Ref Phono, Aesthetix, Manley Steelhead, and I'm sure a few others...