Recommendation for better tube on Vincent SV-236?

Hi, new to tubes and need help with improving sound by replacing the 3 stock tubes in the preamp section of this int amp. What would you recommend?

Picked up ShengYa A10CS (Vincent SV236 MKII) hybrid amp. Got rave reviews on April '09 issue of Stereophile plus years as recommended components at TAS.

One Agoner stated "1963 Sylvania NOS 12AX7s made a dramatic difference in the sound – a bit of glare that I initially had noticed was gone".

Thanks in advance for your inputs to this tube newbie.

Cheers