Would like some opinions on tube rolling

My AudioNote preamp uses two 5687 drivers and two 6x5 rectifiers (I think that's what they're used for...). They are all Phillips. I would like to get a little more bass and mid-bass oomph. The unit is extremely detailed and transparent currently. I'd be willing to sacrifice a little (very little if possible) of that transparency to get the added warmth. Since many here have had good things to say about interactions with Upscale Audio I sent off an inquiry to Kevin, but haven't received any response from him yet. When I do talk with him, I'd like to have a little more background as to the possible alternatives and some input from those who have actual experience with the subject.
Thanks for the input