Preamp for a Line Magnetic i518?

I am interested in adding a preamp to my system. Currently using a Line Magnetic 518 integrated 845 SET. I listen mostly to vinyl with a Chinook phono amp and VPI Prime turntable with Lyra Delos. Speakers are PSB Imagine T3. Any thoughts on adding a preamp and suggestions? Partial to tubes but let me know if there is any ss that would possibly be a better match? Budget approx $3500. I appreciate any/all advice....thanks.
Freesole, I I will let you know about the LM 518 and ps audio bhk combo in a a week or so. I just got the LM and am letting it settle in without adding the pre for a minute 
@akiravelvet awesome, congrats and enjoy! Would love to hear your thoughts when you can share them. 
Surprised no one mentioned the Atma-Sphere MP-3 as a contender here!
@ozzy62 That's a legit question. Both the 518 and 508 don't really pass the preamp section, so isn't adding another PREAMP just adding more stuff into the signal chain?
@divertiti That is what I was advised and just to check, I bought a Don Sachs Preamp just to see if I would hear a difference. The difference was hard to pick out over time. In speaking with the distributor of LM, they have said the same - the preamp stage is not bypassed on the LM integrated amps (508/518/805/845). I have the 805ia.