Audio Research Ref 3 VS Mark Levinson 38s

The 326S is an excellent preamp; I enjoyed having it in my system.  Don't think you can go wrong with it - it is really tough to beat for the price. 

Would the ML 326s be worth the extra 2 grand or so ?

Only you can make that decision.
I am sure that you will be happy with either one though.

I would think that if you are paying an extra 2 grand, the price is either really good on the ARC Ref 3, or really bad on the 326S.
I see them selling for about the same price, unless the 326S has the optional phono stage, and even then it's only about $600-$1,000 more.

Now that is judging by sold prices on HiFiShark, not asking prices in current ads.
So if you are seeing a 2 grand difference, either the asking price for the 326S is too high, or the asking price for the Ref 3 is too low.

Completely agree with @jmcgrogan2  that there shouldn't be a $2k price difference.

Im thinking about the ARC Ref 3 with the speakers i have being the B&W 800 matrix. The majority of the music i listen to is classic rock. That being said, alot of classic rock recordings are not the best. I think introducing a tube preamp to my system will take some edge off the recordings.