Are there any $1500 tube preamps that that can compare with Tubes4hifi's SP14?

Your amp requires 1.4vrms to reach maximum power.  Your sources are all digital which means you are already above 1vrms into your amp.

Let me pose the the question of why do you need a preamp?  Adding amplification that will be deamplified via the volume control can only add distortion.   Have you considered using a DAC with a built in volume control or a passive volume control such as a transformer volume control

Your amp requires 1.4vrms to reach maximum power.  Your sources are all digital which means you are already above 1vrms into your amp.

Let me pose the the question of why do you need a preamp?  

@ajcrocker1 , this thread may help bring you up to speed on the OP's situation. 

https://forum.audiogon.com/discussions/i-m-considering-replacing-my-passive-preamp-with-a-tubes-is-i...

He just tried a tube preamp (AI) and found that it sounded MUCH better than his passive preamp.

Check out Rogue Audio RP-1 tube preamp.

I previously was using the Mod Squad line drive passive preamp. The difference in sound quality astounding. The passive Mod Squad sounded two dimensional  in comparison. And the magical thing was, mind you I have never heard a tube preamp before, was that the  AI connected the note playing with the note that it just passed and to the note that it would it would soon become. It's amazing