Looking for warm tube preamp (should pair well with Pass power amp), budget $6000

@smodtactical upgrading to the GE 6550  is supposed to be smoother and wakes up your AR ref5SE preamp a bit, assuming you are still running the stock tube in that spot. Call AR and ask them about how they use to reference the expensive 6N30P-DR / 6H30n-DP Super Tube in their amps. Some like to replace both the 6550 and the 6H30s.  For Plan-B, maybe there is more to be had out of your current preamp before leaping away. Best of Luck. 

Got it thanks @decooney 

I’m considering a bespoke pre with two 6SN7s driving the output transformers, with tube rectifier and choke. No capacitors in the signal path. More research needed as to the import of this, as others mention capacitors.

Any opinion on evo 400 pre ?

@smodtactical-Call Aric again, have him build you a Motherlode and get off the preamp carousel. No risk, all reward! I have mentioned before, The Motherlode is the only piece of gear I have remain in my rack since the first day of listen.