Jan GE 6cG7 what other tube recommendations

Hi all,

I want to replace my Ei 6cg7 in my pre amp. What are the Jan GE 6cg7 like soundwise as I could get a pair. What others do you recommend? What are the RCA clear tops or grey plates like?
what place do you recommend to purchase them - I live in Australia
Any assistance would be appreciated.

Cheers

Steve.