Best Vacuum tube for Bellari VP129

I've currently got a Ruby 12AX7A tube in, but wondered if there was one that would improve performance noticeably?
The Sovtek 12AX7LPS is very good and not to expensive. There are a myriad of NOS tubes, but they are kind of pricey. Try a Mullard CV4004 from Upscale Audio.
Thanks. I may try that Mullard out. Wonder what the life is supposed to be with these?
I don't think that Bellari runs the tube very hard, so I would say at least 2000-3000 hours and maybe more.
Maybe do some reading in the forums or check out some info that was sent to you regarding other resources for tubes.