I need your suggestion for a Preamp.

I have an Ayre K1xemp....wonderful unit.   Mine has a great phono board, and remote....the sound and service are tops.

That is one great sounding amp, and I am sure it has a wonderful sounding phono stage, but unfortunately, it is out of my reach, even a used  K1XE is going for well over $3500.00.

Benchmark LA4

https://benchmarkmedia.com/products/benchmark-la4-line-amplifier?variant=12552489664629

ML 380S. No experience with the Ayre or JR so probably silly to throw my two cents in but remember the 380S. Great preamp with great resale... I bet in ten years it’ll still pull good money where the other two not so much. You already have two other ML pieces so why not? Very flexible preamp. 

audiomaster

The power amp is a Levinson 431, driving a pair of B&W Matrix 801 S3. I am using a Levinson 390S CD processor to drive 431, the sound is not too bad, but I need a couple of more inputs as I intend to use a TT and add a blu ray player as well.

Your ML431 only needs 1.8v in, for full 235w output!! and is 51k input great for a passive volume control. Your ML390s gives this easily and the balanced 4.7v, and your 801’s are 89db, why not just get a source switch box, and a high gain (60db) phono stage instead
Here is a quality one, there are are many configurations at the bottom of the page with and without VC if you go with a volume get the 5k or 10k one to suit your 51k ML431. http://www.goldpt.com/info.html
With the phono maybe go the SA4M dual mono as phono cartridges are never balanced. http://www.goldpt.com/sa4.html

Cheers george