Dynaco ST70 Tube replacement

I would like to replace the four Amperex 6CA7/EL34 tubes in my Dynaco ST70 amplifier, I am looking for suggestions.
Thank you.
Why are you replacing them? The original Mullards are really nice if you can get them. As for new tubes the SED "Winged C" tubes are good sounding - much better than Sveltlana branded whatevers.

Are your amperex "worn out"? If not, then you will be spending a bundle to replace them. NOS are definitely better than anything new. I have played with most of the russian and chinese tubes and really like the resolution and detail of the svetlana el34's for the money. I have a really inexpensive used quad if you are just looking to play?