Are MULLARD NOS EL34s and LTA ZOTL40 REF worth the price of admission?

I'm considering giving an older Linear Tube Audio (LTA) ZOTL40 Ref amp an audition.  LTA has a factory upgrade that includes upgrading to Mullard NOS EL34s for $800 (or less with additional discounts).  I am wondering if quad set of old-stock Mullard EL34s are worth the $800 price of admission?  I don't pretend to know what anyone else's budget is but $800 for quad EL34s seems like a lot.  If I'm paying the premium, it better be across the board and not just improvements on chamber music or obscure Chinese opera (no offense intended).  Does anyone have experience with either NOS Mullard tubes or LTA ZOTL40 Ref amp?  If so, please chime in.  Thanks.
IMO with my ears, no.
I bought new Chinese EL34s from a local tube matcher in Cleveland and they sound wonderfull in my RAM-9mkii.  I would just start with matched new production Chinese EL34's and see how they sound.  About 160 to 200 for the octet.  I can give you the contact info on my guy in Cleveland if you want.
Amps depend on the tubes. Tubes depend on the amp. Both depend on the system and the CBLF.

Only your hairdresser knows for sure.
I have the Linear Tube Audio Z10 and all I will say is that you should try it and prepare to be amazed. Never heard another amp play music with such clarity and power that is far beyond what the watts would suggest. It’s less Tubey by far than my Primaluna was, but the trade offs i made for the Primaluna are gone. 40 watts on the Primaluna couldn’t match the 10 coming out of this. Just try it and find out. 

So, not sure if this is of any use, but thought I would share my experience with EL34's.

Gone through a pile of them over the past 25 or so years with my amp. EH, JJ's, Psvane Phillips Replica's, Winged-C's Gold Lion KT77's (currently in amp) and some others that I don't remember??? 

Never spent the $$'s on NOS Mullards, was more than I wanted to dish out, and passed on the new production ones. However, that doesn't mean I'm not curious as hell to hear them in my amp...

The Psvanes, quite lovely sounding (open, nice extension), but my amp burned through them- two sets of quads in 18 months? Prior to those, I ran the Winged-C's for years with no problems and they sounded to me as I felt EL34's should sound. Warm, nice mids and tight bass. Would get again, but they have become a bit pricey. The KT77's rival the Psvanes as far as transparency and extension goes at half the price. 

Then there are these...

The nice thing about LTA is that, in that amp, those tubes should last you a life time... I have the ZOTL10 not the 40, but upgraded to vintage 6085s and 7062 in place of the 12AU & AT Xs in the line stage (from the two suppliers mentioned above, in fact--I second their recommendation): wonderful improvement that I do not regret paying for--about half what you would pay. It's a terrific amp either way: I simply wanted to give it the best.