Best sound tubes in Audio Research PH3SE

I have a Audio Research phono stage PH3SE that have the stock tubes. They have been used for many years. I feel it is time to change tubes. Has anybody tried different tubes and found some that sound better than Audio Research tubes. Since they last so long, I am not concerened with cost as much as sound
Hi...yes. I upgraded the tubes to Mitsubishi and I got them from Vintage Tube Service. There was a big difference. More mellow and warmer. However, it retained the sharpness that is needs to feel the bow on the strings ...if you get what I mean!
You will generally find the unit to sound less harsh with NOS tubes. Audio Research distributes Sovtek tubes.

Personal preference and system synergy will have big impact on your choice of tubes. Check JoeS's excellent comparison on many 6DJ8/6922/7308 variety tubes on AudioAsylum. His description of tube sounds provides an excellent reference. People have recommended Tungsrums and Russian 6H23s. I currently have 3 Amperex 7308 white labels in my unit!

I am trying a trio of matched SYLVANIA JAN 6DJ8/ECC88 "Green Hornets." They sound a little better to me than the ones I usually run, a set of Matsushita / National PCC88 / 7DJ8 Cryo'd from Upscale. I haven't quantified it yet, need some more hours. Nothing wrong with the Upscale tubes, they are fantastic...very reasonably priced too at $43 for cryo'd, platinums. I can't tell anything about the cryo part, as I've never ordered any from Mr. Deal that weren't. I just sold another PH-3 running 6H23's, also from Upscale. They sounded great too, perhaps a little more laid back in my system. Call Kevin at Upscale. He can be very helpful. Across three different PH-3's I got too much sibilance/harshness from factory tubes. With the caveat that YMMV, of course.