Question about replacing 12AU7 tubes.


I am new to tube amps and have a question about the 12AU7 tubes in my Dared VP-300b Quasi Monoblocks. Each of them has a 300b tube and 2 12AU7 tubes.
I would like to have a replacement at hand if a 12AU7 tube goes out (also read somewhere the stock tubes are not that great).
Do I need to get matched pair or even 4 matched tubes?
If matched pairs would I put one matched pair in one mono block and the other pair in the other, or would I put one of each pair in each mono block so they have the"same" kind of tube combo?

Any suggestions about this and any tube suggestions would be appreciated?

Thanks.
utah_dude
My experience with 12au7's is as follows- Mullard is my favorite, followed by RCA clear tops. When you factor in price, the RCA clear top is a bargain.
Thank you all for your input. I will think about what tubes to order as a backup/rolling ensemble. I also have not been able to find info about which tube is which for the 12AU7s. I will try to send them an email

I was fortunate enough to get some gently used Sophia Princess Mesh 300b tubes and had ordered new Tesla ECC802S tubes with PLATINUM pins.
When all the tubes were in, I could not tear myself away from the beautiful sound (some Stacy Kent, Patricia Barber, Diana Krall, Ella Fitzgerald, Johnny Hartmann, Gillian Welch and more) and also could not get the big smile off my face.
I definitely want to get some backup tubes because I cannot imagine being without this if a tube should go.
When I first got my VP20 I went a little crazy with tube swapping. My favorite 12AU7 ended up being a set of Sylvania 12AU7WA mil spec tubes I bought on ebay. I knew they had never been opened as they came in the boxes I remember tham coming in back in the day when I was an electronic tech in the Air Force.

Actually, the nostalgia of seeing those old boxes with the federal stock number may have had a positive influence on how I heard them. They seemed to have the cleanest sound of all the tubes I tried and I have read on other forums that those particular tubes can sound less "tubey" because of their clean high frequency presentation.
I was thinking about picking up a pair of those Dared VP-300B to power my tekton speakers. How do they fare against the previous amps you were using? Are you coming from solid state or something else?