Better amp or better tubes?


With this lockdown I'm finding myself and I'm sure many others listening to music more often and with that my mind has gone into upgrade mode.
My amp is a rare Quickilver 300B that must be at least 25 years old using genalax gold lion  300b tubes.
Over a year ago I sent an email to Mike sanders asking him about suggesting upgrades to the unit and surprisingly he told me if the amp is working fine to just leave it alone. We ok then.
The genalax 300b are modest in price  costing about $300 a pair and have worked flawlessly. If I were to upgrade the tubes, what direction would you suggest? To be honest, I'm a bit apprehensive in spending a lot for tubes since they can fail at anytime. Am I being overly concerned?

So, do I upgrade the tubes or amp? Amp budget of under 4k.

Thanks


emil
There is a big difference in terms of sound profile when you get into better 300Bs.  As someone who imports 300B amps, a big question is what tubes to go with.  
At a modest price, the Emission Labs 300B is a huge step forward from the Russian mass produced tubes and is what I ship standard with out Diavolo amps.  These are $675.  

KR tubes offer a bit...more.  More detail, slightly better linearity.  Tighter bass but are a bit more expensive.  The base 300B is $1100, the balloon which has a larger envelope is $1300.
Sophia which are largely TJ Fullmusic are wonderful tubes. Last I checked, they have the Blue glass classics in-stock.  Those are best with the matching 274B.  What rectifier does that amp use?  They are out of most of their other 300B tubes but they said the have a few Royal Princesses in stock.  The blue glass are $1000 with the better warranty.
I sell these three brands at ArtAudio.us
Acme PSVane has a great line of products and only in the US, only sell direct.  Lots of threads covering off on different variants to dig into.  One note.  Anyone claiming they are selling new PSVane/Acme tubes better be reselling a pair they bought or their is a chance they are counterfeit.  Evidently this is a big issue on eBay for them.  Go to their site to buy direct.  

Takasuki’s are amazing tubes but a bit pricey.  Made in Japan, these are stock tubes on the Luxman 300B and are one of the best current runs.  The only issue with these is they tend to perform best at a lower bias.  They aren’t as sensitive as the EML Mesh which max out at 28w as opposed to the standard 40w but operate best running a little lower. These typically are priced at $2K a pair from what I have seen.  

I have an e-mail out to them to get a price and terms for importation.  There are a few current dealers. 
NOS 300Bs tend to be pricey as you know. I would be cautious about who I bought from.  

Hello Emil!  If your amp uses a 12AX7 input tube, change it to a New Old Stock Telefunken 12AX7.  I have a 300B tube amp, too and the new input tube made a remarkable. The distributor of my amp (Ele-Kit TU-8600B) says the other tubes don't make enough difference to bother with. At $200 or so, it's not expensive for the big improvement it makes. Keep Smiling.
Thank you all for your input. Much appreciated and something to think about.
@atmasphere 
all tubes have been purchased with the last 2 years with moderate use. I think they should be fine
@decooney 
Upgraditis. Too much free time on my hands. I can easily live with what I have now but isn't this the nature of the hobby?
My system:
Audio Mirror Tubadour III SE
LTA Microzotl Preamp
Quicksilver 300B amps 
Volti Audio modified Khorns
Full Loom Triode Wire Labs cables
@boomerbillone  
Input tubes are 12FQ7 . Recently replaced and purchased from Vintage Tube Services
Rectifier tubes are genelax Gold Lion 5AR4
@Verdantaudio
The Emmision Labs 300B looks like a tube I would be comfortable with considering it's price.

all tubes have been purchased with the last 2 years with moderate use. I think they should be fine
@emil  The age of the tubes and how much use they've had has nothing to do with whether they are good or not. I've bought plenty of bad tubes that were brand new!
@emil
decooney, 
Upgraditis. Too much free time on my hands. I can easily live with what I have now but isn't this the nature of the hobby?

Sure, it can be. Or, until you achieve the title of your post and what is most engaging for you by the way of "better amp" -and- "better tubes" :)