Might try a tube preamp

@bbreneman1   +1 for the Backert Preamp; I use the Rhumba 1.2.

Excellent sounding preamp that's highly tunable based on the relatively inexpensive 12au7 family of tubes (uses a pair). Highly recommended!

These are all solid suggestions.  I would go with the Rogue. Great sound stage, imaging and detail. Also really friendly for tube rolling.  I have owned some of the units listed and when I was in the market for a new Preamp I compared Rogue with some of the units listed as well. Obviously I ended up with the Rogue. 

Nothing against the Rogue, they certainly do make nice equipment, but the most neutral 6SN7s are the Shuguang Treasure 1's, aka CV181T. I am sure that New Sensor will come out with something in their Gold Lion or Mullard line soon that competes, but that is the most neutral tube I have ever heard. If you are tube rolling beyond that, you have other issues in your system, and tubes are a bandaid. Like I said before, the Freya is a nice little preamp, but for it to compete it needs Ken Rads for proper tone, and early 40's Raytheons for imaging. You could use the CV181Ts for imaging as well. The point isn't to roll tubes, the point is to get your system right so that you don't need to!

I’ve owned a LOT of preamps and I consider the Freya to be a neutral, very well designed and way underrated giant killer with performance and features absent from really any other preamps at any price, although I haven’t heard every other preamp including those from Don Sachs, Don Juan, or Don Ho (Although I did sell a Fender Twin Reverb amp with JBLs and an Anvil case to Don Ho in maybe 1980...that’s another story). In my Freya I prefer some recently acquired NOS RCAs and NOS Sylvania "chrome domes" (although I’m not 100% sure the RCAs are better than the Sylvanias, but they’re in the somewhat less critical "output" stage). With these it certainly "competes," and if you don’t tube roll how the hell are you going to know which tube works best with your rig? Note that regarding cost, my Dennis Had "Inspire" Firebottle HO (it’s a HO...says so right on the front) was 4 months old when I bought it for about 1100 bucks, and the Freya new was 700...with $11,438 spent on 6SN7GTBs used in both. So I now have all of this for around $13,238. Take that Don Sachs! (is that like Don Juan? I hope it is if only for my sake). I’m running out of storage space for the tube collection, and may have to wire them up in a string as holiday ornaments.

Take a look at the deHavilland Mercury 3 preamp at $4500.