Changing Tubes

More air and bigger soundstage if possible 

Change out EH 6SN7 out of my Atlas amp  with Tung-sol 6SN7GTBs

Haven't done any tube rolling was amazed at the change in the amp

more air and bigger soundstage

Email Brent Jesse for advice.
http://www.audiotubes.com/

Mention what preamp you have, how many tubes you need, what sonic characteristics you’re looking for and your budget. 

I’ve gotten tubes from Brent in the past and he was always spot on with a recommendation. Good luck!

Tube rookie here, what is it when a tube goes “microphonic”?

When a tube is upset mechanically by external vibrations and those are passed into signal. Due to construction most signal tubes are inherently microphonic but their location on a board can expose this phenomenon further.

Effects are feedback, ringing, hiss, rattle noises, static noises, distortion, high pitch noise, anomalies in frequency's response.

More air and bigger soundstage if possible 

bigger soundstage = siemens, voskhods, reflektor

More air = amperex, raytheon, french made 88, tesla, telefunken

Above are only my general observations and as  i am not familiar with your preamp you may find something that fits your requirements better.