http://www.audiotubes.com/el34.htm
You might consider a quad of the 70's Chinese EL34's listed @ the bottom of the page for $160.
Mullard XF2's look to be around $800/quad.
DeKay
Do NOS Mullard EL34 tubes last much longer than NOS SED (Svetlana) EL34 ?
Well, Mullards are $450 each and SED are $120 each. I need four of them for VAC Avatar SE. For now I got a set of SEDs but for the next set..? Bloody expensive. I really like Mullard long plates 12AX7 for line amp.
Maybe it's not worth it, anyway, maybe I wouldn't hear much of a difference.