Tube pre amp

Have two power amps a Ocm 200 and Emotiva Xpa 2 Gen 1 . Thinking of getting a tube preamp
one in mind is a Vincent Sa 31.

Would this be good match and what kind of sound stage and detail could be expected?

Ask Ralph Karsten how much he is asking for one of the several versions of his  Atmasphere UV-1 preamp.  It too uses 6SN7s and can be configured to your needs.
NOS ans ANOS  6SN7s in good condition are still available by the millions or so it seems on the secondary market.  They really do have a specific or characteristic sound, the prices fairly low still* and therefore fun to roll.*Except for the most sought after manufactures and types, for example, the well known and worshiped 6SN7GT Tung Sol round plate.  The TS round plate in ANOS quality can get about $400 +/-.
Troll extraordinaire is correct...
"The Freya is not that good."  
It is VERY good and at the price a screaming bargain: very flexible in terms of inputs and output modes; a balanced design; an excellent, finely graduated volume control; with properly screened tubes (whether NOS or new production, e.g., EH or TungSol) it is very quiet; regardless of tubes used, it's dead silent in Passive or JFET mode.  I use mine with a number of different amps (Taranis, Hegel, First Watt) and am extremely happy with the results.  It supports excellent quality sound with nice 3D imaging.  Highly recommended for an in-home trial, at least.  Can't compare to the Vincent SA31.  Did find it better than the dual 6H30/EZ80-rectified tube preamp I had previously.
Schiit Freya,
i am a Schiit fan. Remember that Schiit sells direct, no middlemen, so the price is about 1/2 of what it would be from a refular AV store. 
That is a big part of their value. And the engineering they are doing in their products is intelligent, sophisticated. 

And you get a 30day trial with full refund. What is not to like??

but I would also support the Vincent tubes and hybrid gear. 
Well- built, very good sound, undervalued and underpriced. 
I'm now on my third piece of Schiit gear as, based on very positive reviews and my experience with my other two Schiit items, I just bought a Mani 3 headphone amp (as everybody should for 100's almost free) a Freya, the amazing Loki EQ, and a Mani 3 for less than a grand should make more than a few other companies somewhat worried as all three are superb sounding, quiet running, no nonsense designs. I did not expect the Freya to be "that good" until I put it in my rig last year, and is that good.
Not long ago I purchased at few tubes from Upscale Audio so now half the Web sites I visit have advertising banners from Upscale.  Anyway they are really pushing the trade in's, a few pretty nice pre-amps.  Their site may be worth a visit.