Seeking advise on 6922 tubes for a preamplifier..

Hello, I'm seeking advise on replacing (5) 6922 Sovtek (I think) tubes on my preamp -these are stock cheap tubes that came with the unit I bought used and I'm wondering of a reliable place to find replacement for these and also which kind to replace them with in terms of brand and model.

I've heard of some horror stories of buying on ebay and yet the thought of replacing and trying different tubes is quite exciting.

Any suggestions?

Thanks