Adding tube sound to my SS system

You might want to look at something different than your T2. I had one for a bit and loved 8 out of 10 tracks but really got tiresome after a bit. The Cary 600 or 700 will sound much better or a Bricasti M3 w/network card will sound much fuller sound and larger soundstage. You may miss a little top end energy at first but when you get used to it you will love the ease in which the music plays. Sabre dacs can be ruthless on a system. 
All the above mentioned streamer/dacs are under 3,500 on the used market so you  won’t be putting a lot dough out of your pocket. 
 

@curiousjim

I also have the BHK Signature preamp followed by 
Pass Labs X260.8 Mono Amplifiers (2)
Martin Logan Expression ESL 13A Electrostatic Speakers.

I understand it has two 12AU7 dual-triodes tubes.
The original tubes have many hours on them;  I use the preamp daily for Home Theater and 2-channel sound.
Questions:
1) What would I hear when the tubes need to be replaced?  In other words, how do I know that I need to replace the tubes?  Everything sounds fine to me now.  This is my first tube anything.
2) There seems to be a lot of 12AU7 tubes available by many manufacturers.  Which manufacturer would you suggest?
3) You stated  “In the preamp I’ve tried 5-6 different tubes and have been using NOS, RCA clear tops for the last couple of months.”  Can you give me ideas of what you heard with the different tubes you tried?   
4) Does using the unit in the home theater bypass cause any wear and tear on the tubes or are they not involved in the action?  The preamp is on doing home theatre duty the majority of the time.  I do not get much time to listen exclusively to the 2 channel stereo. 

Thank you for your help

This is not very High End Audio of me, but let me offer another solution that is cheap and fun: The Joilda (Fosgate-designed) Foz SSX. I bought one for use with headphones when I had a job that would take me away from home for two months every year. 

It can go between your preamp and power amp. It does three things: it is a tube buffer, and changing its single 12au7 tube has great and fun effects on sound. It has a bass control that I think of as a thickening agent, as it increases the bass, and also thickens the lower midrange just a little. And it has a crossfeed circuit (that's the Sound Stage Expander, or SSX portion) that lets you play with the width of your soundstage. 

Again, I used it for headphones so I could have some control over the soundstage of my phones, while adding or subtracting bass. And to warm up my good, but somewhat cool headphone amp.

Recently, I have tried it with an inexpensive solid state amp, and I can't get over how much it improved the musical enjoyment, and at a relatively low cost to fidelity. Might be fun for folks to try. We can't be purists all of the time... 

I jumped into to tubes in 2007 with a Primaluna Prologue II.  Slowly added more tubes-phono stage, tuner, DAC.

I now use a 4 watt Decware Mini Torii with the same speakers I used with the 35wpc Primalune: Reference 3A de Capos 92db.  Plenty loud if you still want to keep your hearing. 

My CDP is not tube but my DAC is an MHDT Stockholm, very sweet musical sound.  My phono stage is a Hagerman Cornet II.  easy to maintain  fantastic to listen to.  Also had a second tube system with Klipsch Quartets run with a 6 watt Grommes.  Again musical.

https://tmraudio.com/components/preamplifiers/modwright-analog-bridge-tube-buffer/

@jbuhl  Yep - the "Analog Bridge" by ModWright is a fantastic suggestion for OP that shouldn't get buried. And Dan Wright is truly a great guy. I almost picked up one myself, but I'm such a gear hoarder and already have so many tube components - I'm not sure I have a use case for it yet. Seems perfect for OP to try. 

A lot of tube preamps use something like an Alps RK27 pot (aka "Blue Velvet", or its motorized version), which always audibly penalizes sound quality (even if slightly) whenever I've compared it to other alternatives. Even up to very high MSRP's, you see that ubiquitous blue plastic pot all too often. I hate it! I absolutely hate the Alps Blue. I can't understate that. In general, the volume control is often a weak point of the tube preamp. The Bridge avoids that issue.

I was running a Rogue RP-7 tube preamp into a highly-regarded Rogue tube power amp, the power amp replacing a SS amp driving my Fyne Audio F-702 speakers that were made in Scotland.  I felt it resulted in degraded tonal qualities of instruments, reduced definition, and slightly reduced soundstage.  I replaced the tube power amp—but kept the tube preamp—with a pair of Odyssey SS monobloc amps, and I have regained what I lost plus gained better imaging and depth and lateral dispersion of soundstage. 

@mike4597 Most of the Rogue power amps (I had Apollo Darks) do not sound like traditional tubes. And the RP-9 didn't sound even *slightly* like a tube preamp to me (like the RP-7, it's actually a hybrid). I've had Solid State amps that are actually "sweeter" sounding. Glad you found what works in your system! Nice speakers.