Tube upgrade for VAC Ren 30/30

Hi all,
Now that I can finally start dabbling a bit in in higher end analog audio, I had a few questions to ask of the community. First up is one regarding tube upgrades. I'm quite new to world of tube-based amplification, and after much research and auditioning I'm just finishing up building out a system that I think will work for my needs.

I've got my hands on a VAC Renaissance 30/30 MKIII amp with the Signature circuit upgrade, and now have that paired with a Shindo Monbrison preamp. I'm very excited about both of these! In my opinion, the Shindo has a very nice tube compliment out of the box. As for the VAC, it is currently fitted with the stock tube compliment-Four Chinese VAC-tested 4-300b output tubes, and four Chinese Golden Dragon 6SN7GT low level tubes. They sound quite good, but it seems I can realize some additional benefits by experimenting with the tube compliment there.

Of course one day if I can ever get my hands on (and afford) a matched quad of NOS WE 300b's, I might like to go that route for the output tubes, but let's assume that's not happening any time soon. However, the research I've done suggests you can acheive real sonic improvement with replacement of the low level tubes, at considerably lower cost. So that's where my search and my question lies:

For the amp/preamp setup that I have (my musical tastes are all over the board, but I like a lot of vocal and acoustic-based content. Lots of Blues, bits of Jazz, some rock and electronic. Equal digital and vinyl), what suggestions might you have as a low level tube compliment for my VAC? I have read fantastic things about the Russian military NOS 1578 metal based tubes. I've also heard great things about the Russian 6H8C military tubes (with metal base and black t-plates with holes), which I understand is very similar to the 1578. Other tubes that have come up with favorable reviews in my research have been the ECC32/ECC33 and CV1988 tubes of British origin (Mullard, others), the famous Tung Sol round plates, and the RCA red base 5692's. Most recommendations were that NOS from the 1950's was most preferrable. Does that match with the findings any of you have had in tube rolling with comparable equipment? Keeping my components in mind, are there options above that you would recommend over others? Or others I haven't mentioned?

Of course I know that the "best" sound is completely subjective and based on listener preferences, components, and room acoustics, but I'm just trying to get some insight from folks who may have had more extensive experience in tube rolling, and hopefully I'll be able to use your feedback to form some baseline opinions of my own as a starting point in searching for items that are both hard to find and difficult if not impossible to audition live before committing to. I definitely won't have the money to swap out tubes very often on an experimental whim, so I'd like to start off with what I believe might be ideal for my needs. I know, I know, an audiophile pipe dream... :)

My system will be as follows (literally, I'm *just* getting all the pieces in place):
Speakers: Verity Audio - Finn
Amp: VAC Renaissance 30/30 MKIII-S (Signature circuit upgrade)
Preamp: Shindo - Monbrison
TT: Rega P3, RB300 arm, Benz-Micro Wood SL cart
CD Player: To be upgraded, but currently a Cambridge Audio 640C. (Still looking, but potential frontrunners are the Doge model 6 or possibly a Naim CD5i-2 at this point)
Music Server: Cambridge Audio
Cabling: Auditorium 23 speaker cables, Shindo Silver ICs for preamp-to-amp, and a mix of Siltech, Harmonic Technology, Shunyata, WireWorld, and Ultimate Cables elsewhere for IC and power cord needs (not 100% sure which cables I will re-use with each component yet; have to trial them in different setups).

Thanks so much for your time, and for your insights. I truly appreciate it.

I'd send an email to Audiogon member "Raquel". He is quite knowledgeable about VAC amps, tubes, and particularly the amps you own.
I would suggest living with your system for a while and try to find out what is missing and that will allow us to recommend a tube with the missing attribute.
Brf has a good suggestion.

Frankly, having owned two VAC amps in the past, I have found the stock Chinese tubes supplied with the amps to sound excellent, and difficult to better (but not impossible of you have deep pockets and are willing to spend for subtle improvement).
Thanks, guys. Good point, for sure. My initial thinking was that I've got quite a bit of gear and cable burn-in time ahead of me, and if I could burn in a set of tubes simultaneously to have something to compare against afterwards, all the better. Also, I was thinking that it could potentially take a few months to find a NOS matched quad from a reputable source if what I'm looking for is a bit rare, so I'd have a head start.

But yes, your point is well taken and there is certainly all the benefit in the world to spend some time with the system and observe performance across a wide range of musical content.
Touch base with Andy Bauman/Vintage Tube Services Or Brendon at Tube World.
If Andy has what you need,he will take back those that are well cared for and not abused (refund).But please discuss this subject with him.The initial outlay could be rather sizeable,but you have them handy to interchange.Keep your preferance and return the others.
I have a Ren 30/30 Signature as well, my favorite amp that I have owned so far. I actually like it better than a Phi 300.1 that I briefly owned, if that seems possible. The 30/30 has got a very satisfying, 3D and musical sound coming from the 300B/6SN7 combination and whatever Renaissance circuitry that makes them work.

I actually like the stock tube combination, overall quite musical and holographic sound. Overall the stock combo is not very easy to beat and is the most worthwhile set of tubes for the money.

However, after tweaking around, I now have a combination instead of Sophia Electric carbon plate 300B with Tung Sol round plate and Sylvania 6SN7W metal bases. This combo is more neutral sounding, dynamic and cleans up the sound while still sounding very musical. The difference to me is very easily heard. However I probably spent well over 1500 for this tube combo, so you would have to decide if it's worth it or not. Also my Chinese tubes were probably closer matched and therefore quieter with no music playing/preamp muted, but can't tell when actually listening to anything.

I've also tried a set of newly available Sophia Electric 6SN7 tubes. They appear to be very well built and sound pretty good, just not as good as the best NOS.

Also I have some of the Russian 6H8C purchased for another component, but these are not the 1578 type with round holes. If you search on this, more than a few people say the real 1578 are distinctly superior. I have never heard the 1578, but the ones I have I felt were nothing special as far as sound compared to Sylvania or Tung Sol.
I agree with Tvad...I have owned 4 different VAC 30/30 amps over the last 12 years all the way up to the Phi 30/30, and have rolled a lot of tubes in them all. I certainly heard differences between them, but none were clearly better than others...just different. Kevin and his crew have spent years voicing these amps around the stock tubes, and I have always gone back to them in the long run. Save your money or spend it on something else in your system. Stick with the stock ones!
Thank you all for the thoughts and feedback. I will likely spend a little time with the system, and continue to research potential paths for eventual tweaking, and post my comments when I decide to give something a shot.