First Watt SIT-3 preamp pairing advice

Also want to second what Nelson Pass said, and which @vinpic highlighted earlier in this thread: the SIT-3 behaved like a different, happier amp when I wired resistors in parallel with my 8 ohm speakers to drop the load the amp sees down to 4 ohms.  I felt kind of dumb trying this with 8 ohm speakers, and wasn’t expecting much, but it definitely improved the overall presentation, which was already excellent. A fun, inexpensive tweak to try.

My advice would be that if you are looking to land on the cooler side of neutral rather than full-on classic tube bloom, the LTA would be the better choice.

@zm I have read this so many times from so many people that I take it as fact. 

The LTA is great, but falls "on the cooler side of neutral" as you state.  If you're looking for warmth, it's not the place to go.  In that case the Don Sach's is a good candidate.  I have owned and loved one.  Note that its sound is heavily determined by the the output capacitors and tubes used.  You can read on my system page for some information in those regards if interested.  My speakers aren't naturally warm (accuton drivers), so adding a cool-leaning preamp is a no-go for me. 

I suspect the Supratek sounds similar to the DS, but gives you a higher gain option, and has an external power supply which is a + in my book.

I have to put another vote in for the Supratek.  I have the Cortese LCR.  I drive Rethm Saadhana (100 dB sensitivity).  Cant say enough about the sweet sound.  I prefer analog, but do listen to a lot of Qobuz/Tidal due to me limited vinyl collection.  My ExoGal Comet DAC does help keep streaming more analog sounding also.
And value of Supratek is outstanding!

Thanks @cal3713 for your impressions! Very helpful. And i tend to agree that anyone that spends time on creating a highly engineered outboard power supply likely has a good product. I am in the camp that a good portion of the sound (quality) of a piece of audio equipment comes from the power supply. 

The MZ2 has more air and transparency. I would agree with zm's characterization of the MZ2, but it still has that tube liquidity. I do think the other 2 choices are good pieces, and I still haven't sold my Supratek Sauvignon . I've been thinking about building or buying a Don Sach's phono stage.  My MZ2 has remote volume control and an external power supply, they are both options and it is considered a Stereophile A rated headphone amp. With  both options it costs a little over 2K. The pictures of the MZ2 don't give the fit and finish of the unit justice. I believe the case work is done by Fern & Roby. It is very well built.
I was going to purchase the Pass HPA-1 but it doesn't have a remote control. As I'm writing this response, I'm listening to Ronnie Earl and I feel like I'm in the studio/hall with them.