OK, lets see.
A new Ultra SL with phono is $1848.
Your Transcendence Seven SLR with phono in the small SL chassis will probably bring $800 - $900 used if still in like new conditon. We take 15% to broker the unit. Lets assume worse case $800 and that would be $1848 less $680 net for your unit or about $1150 difference.
Upgrade is $1099 because all three boards have to be removed and sigificantly reworked or replaced, heavy labor time.
The new unit remains better because it has the new one piece mother board with eight regulated power supplies (four are the most we can squeeze in in the small chassis) and the new mother board has a better low impedance full ground plane layout. And of course it has the new big SL chassis with the potential for future upgrades in the distant future - - - nothing more short term, we have "fired our big cannons" for a long time now.
Soo -- it looks like it would make more sense for you to trade up. Of course I would advise you to start with ebay for resale of your T7, you might do better there than we we can do.
However, I am absolutely out of used preamps here right now so I suspect I would get $900 for your unit pretty easily now.
Hope that answers your questions.
Frank