Used preamp under $400...

I see others have beat me to the punch, but I'll say it anyway.  Schiit Audio Saga +.  You can also get a b stock version for a little less.  I've had the old gen Saga, which was my first passive.  It was so good I thought I'd try out the Freya +.  I'm not disappointed!  

The old Saga was better than my Parasound Halo P5.  They refined their pre's significantly so I expect that the new Saga + would be even more of a giant killer.

for $400 you ain;'t gonna get much.

hi the schiit saga+ is passive 

rufust OP
Thanks George, that is some great info. I will check that out right now. Would you have a recommendation of a non colored pre that would fit the bill?

Yeah after trying the passives on the back of the amp first and liking it, I’d go for this as it has a very good 128 step relay remote controlled volume, and it has an active stage "should you want/need to use it".
There is the Saga tube/passive for $399 but I don’t think it has as finer volume steps, and as for the active stage, I’d rather the solid state/passive option of the Freya.
https://www.schiit.com/products/freya-s

These are also good for a little less but no remote, and no active option, and the volume control is not quite as good as the Schiit Freya’s
https://www.goldpt.com/sa1.html

Cheers George

As ‘yogi’ noted, I purchased an open box Parasound ZPre3 For my 2 channel listening and am very happy with it. It was bought fully warranted at your price point (actually $350 from Safe and Sound). It’s impressive for the cost.

The ZPre is basically the Parasound Classic200 without the DAC or phono stage built-in.