Upgrade option from an Audio Research PH3?

 Glad you like your new LS25 mk2. It really is a wonderful preamp. One of ARC's really ground breaking designs. It still holds it's own quite well against newer preamps.

 Tell us about the rest of your system including power cords and cables. What kind of table do you have, MM or MC? 

I have a VPI Aries with a Dynavector DV-10X5 Moving Coil Cartridge
Mark Levinson 532H Amp. 
I am using Nordost XLR from the amp to the preamp. The rest of my system has MIT cables.