Might try a tube preamp

It’s clear from your post that you are new to tubes and your intent is to introduce tube sound to your system to see it’s right for you.

My advice:
1. Buy a tube amp to fully experience tube sound not a tube preamp to use in front of a SS amp.

2. When moving in the direction of tube audio for the first time do not buy new, buy preowned.

3. When selecting a tube amp be aware that the equivalent sound/usable power ratio compared to SS is about 4:1 meaning a 200w SS amp can be replaced by a top brand class A 50W tube amp.

Check out the pre-amps from Backert Labs.  Well within your budget, great build quality, and they sound fantastic.

@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!