Preamp Recommendation

I have just purchased Classe CTM-600 Mono blocks. They are currently running with an old ML 38s. I have tried using a VTL 6.5 III but had a hum problem. Tried everything but could not get rid of the hum. The 6.5 was not new so the pre it self could have had problems. 
I have an option to buy an Ayre KX-R at a great price. Question is will the Ayre a significant upgrade on the ML? Speakers are B&W 800 D. Sources include Clear Audio TT and a PS Audio Directstream Junior. 
Congrats on your Classe's.  Have always liked their amps.  It is too bad you couldn't solve the hum issue with the VTL's, that sounds like a great sonic match.

I cannot answer your question but would recommend you try tubes in the linestage and even phono stage.  The Classe has a high input impedance giving you lots of options.  I always ran tubes with my Classe amp and Thiels - your B&W's are similar in the top end and might really benefit from tubes.
If the Classe has a balanced input, I would take advantage of it. BTW there are balanced line tube preamps.

Also, do be careful with that Classe. Some of the output devices have gotten hard to find.
Srafi are you located near Chicago, Il?
You did not mention price , SS or Tube  preamp.

Myself recently just got away from main stresm commercially made. I decided to try a Direct Heated Triode preamp 
Using premium everything ,4 pole power capacities Lundahl transformer based with multiple filter chokes. NEOTECH 0 crystal 
Wire. The sonic purity is outstanding. 
This is exactly why I custom build. Using high-end parts for much better sonics.😎 nice to hear someone else has broken away from the norm!👍
Parts Connexion has a 25% off sale this weekend, and free shipping over $100.
Have you listened to a Primaluna Dialogue preamp yet?

I haven’t but if someone has one and is local to the Chicagoland area and wants to demo it. I’d take up that offer. Love to compare mine with it. They are 
Sorry, hear it with my tube preamp
You know, I wish it wasn’t integrated rogue did this. They also made one without kt120’s. The intergrated one sounded horrible, it was the preamp that sounded bad. Now coupling the amp without the preto a seperate component as it was much better sounding!
I use the Towsend passive with either the Gamut 200 or CJ 350. I also have the Audio Flight which is  very good
I think there's a certain darkness and quiet of the Ayre designs which would work very well with B&W speakers, but should listen. :)
I like the 👀 of that gamut! As far as preamps passive is really good but I like a little gain and tube dynamics. Doesn’t anyone use tube amps? Just kidding!😊
The Ayre will be a rare experience.
Due to the Teflon boards, it needs run in playing music for 4 to 7 days
once it's done it will be obvious how special it is.