New PrimaLuna versus used Audio Research preamp?

only ARC preamp I like is the Ref 10. the LS series is sterile and SS-like. 

I'd try a Primaluna first and roll the tubes. or an LTA MicroZOTL.

“the LS series is sterile and SS-like.”

This is why many make the distinction between the LS and Reference series of ARC line stages. They aren’t one and the same.

I haven't heard the newest Primaluna gear, but my impression of it over a couple of extended listening sessions that it was more "tubey" and very euphonic.  That is what got me interested in tubes actually.

Having said that, I own a LS26 and a Vsi55 ARC integrated, and have heard Tomic601's 5se.  

If you have the funds for the 5se, jump on it.  It's likely to be an end-game piece, and if it's not, you'll recover most of what you spent for it if you're buying used, while even heavily discounted, the PL will lose a lot of it's value if you try to flip it, which you will probably more likely to do.

Some other options to consider.  The Modwright preamps are really nice.  I owned a LS100 for a long time.  I replaced it with a Herron Audio VTSP-360 which I highly recommend.

Big Greg the PL will not lose that much value especially buying used.  I sold a PL Dialogue Premium integrated a few years ago for not much less than I paid for it new. Currently I have a EVO 400 preamp and it's been a joy so far. One of the best things about it I can roll tubes to change the flavor somewhat which is something ARC can't do with the 6H30 based models.  A dealer did tell me and take it for what it's worth,  several of his customers were trading in their Ref series preamps for the EVO series. How high up the Ref chain I do not know but I'm guessing Ref 5SE and down.  

@samzx12 It looked like the OP was weighing a used ARC vs. new PL.  That's great you got most of your investment back when you sold your PL.  Typically, you're lucky to get 50-60% of new price on most items.  I think Primaluna has a lot going for them.  I prefer the looks, sound, and build of the ARC.  Others might like the PL better for the same reasons.