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
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?
HiGodachilles,
Before the VP300, I was using the Peactree Nova as my DAC, Preamp and Amp. I am still using the Nova as a DAC and Preamp, but have replaced the Amp section of the Nova with the VP-300b.
I have not done a side by side comparison, but my impression is that the Soundstage has improved (clearer), and the detail I perceive in the music has increased. Almost like a layer between me and the music have improved. While I feel that all music has improved, I find female vocalists particularly stunning (Stacey Kent, Patricia Barber, "les moulins de mon coeur" by Carmina and many others).
Be aware that the VP-300b comes without 300b tubes.