Buy 12ax7 tube

First of all, I must say that it's preferable to buy tubes from a reputable dealer who's stock will be high quality and guaranteed. Tubes from a Chinese website may not be genuine or may not test as new or NOS. There are plenty of good, inexpensive dealers on Ebay.

Regarding your tubes, I see the Vincent uses 3 12AX7s (ECC83) in the preamp stage. I assume you are  replacing all 3. 
Telefunken are the most neutral and linear, but expensive. RCA Blackplates are affordable and offer a sweet midrange with good dynamics, $40 to $50 each. Raytheon is a low noise tube with open sonics. I would choose these NOS tubes over Genalex.

You'll want these tubes to be matched since they're in the preamp stage.

A reference for the 12AX7...
https://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html#12AX7

On Ebay, Viva Tubes is a reputable dealer with good prices.
Brent Jessee has everything.

Don't discount these for new production. They have bested a lot of NOS in my phono pre
SVETLANA 12AX7 

Most of the tubes I get are from Brent Jessee; have also bought from Tubeworld. I think the guy is Brandon. Good products from both.

That's interesting about the Svetlana 12AX7. They are famous for making the highly rated  Winged C EL34.

lowrider, I think that the company that made the the SED Winged C El34 (the old Svetlana in St Petersberg) is not the company that took on the Svetlana name and now markets the 12AX7 and other tubes labeled Svetlana. I don't think that the St Petersberg Svetlana ever made a 12AX7. If they did I missed it. :-)