The Cryoed 12AX7 were not as good as I had hoped. The Cryoed 5814 Sylvanias sounded very, very nice but did not have quite enough gain. So much for the Cryoed ones for now.
I currently have GE 5 Star 6201 in there and they have impressed me. 6201 are military spec 12AT7. They bettered some Raytheon 12AT7WA I had. For want of a better term the 6201 had a more "spacious" sound (larger soundstage and more air around the intruments) then the 12AT7.
The GE 6201 were 20 bucks for a quad on EBay. I have some Sylvania and Mullard 6201 en route from Upscale Audio.
I'd say stay away from 12AX7 as you don't need the gain with the TAD150. Use a 5751 instead (military spec 12AX7 with lower gain, similiar to a 12AT7). Since the pre comes with a 12AT7 it might be best to stay with them (12AT7WA, 6201, 7728, ECC801). If a 12AU7 gives you enough gain you can use them (5814, 6189, 7730, ECC802).
I had asked Paul @ Bizzybee about 5751 and 5814 and he said they would be good choices. He does not believe in leaving the TAD150 on 24/7. I use mine with an Odyssey Stratos Extreme that I leave on all the time but turn the TAD150 off when not in use.