Audio Research Ref 10

I´ve bought a set of upgraded tubes for my ARC Ref.10 from thetubestore.com
2 Winged C (SED) 6550C´s unmatched (they don´t match this tubes anymore) and 10 matched EH 6H30Pi Gold´s
I`m a little concerned about the unmatched 6550´s. I´ve being told by the people of The Tube Store that there is not going to be any problem at all, due to the fact that they will be working in the power supply unit, and not in the audio part of my preamp. Is this ok?
Thanks in advance for your help.