Tube rolling Question

Hello Tube Rollers
I recently bought my first tube preamp (Blue Circle 21.1). I've noticed I am need of new tubes as the tube whoosh is considerably more noticeable now than 6 months ago. The amp comes with  Electro-Harmonix 6sn7 tubes which I appreciate and dig the sound. I will certainly replace these with a the gold pin model as I like the sound profile. Here's my question:

What other tubes might you recommend for a different "flavor" of sound, and just to have fun with. I am a poor audio guy so please no recommendations for tubes that will cost more than preamp. 

Thanks in advance.