12AX7's & 6SN7.....

I recently purchased a Consonance Opera M99 integrated. I love it. I am now wanting to replace the tubes that came with it with NOS tubes. I am leaning towards Telefunkin and Mullard, but was wondering which will be the most quiet? i get a good little hum coming from my speakers now, and i'm aware that it's the nature of tubes, but which tubes should i use to get the buzz to a minimum?? it came with Sovtek's 12AX7's as the first SRPP stage and Shuguang 6N8P's (6SN7's) as the driver stage. thanks for any info you can provide...