Upgrading my Sovtek 6922 vacuum tubes

I realize that tube rolling is probably the most subjective discussion on this planet. However, I need some help. I'm currently running a Pathos classic one (MKII) integrated amp that uses Sovtek 6922 preamp tubes. They sound good, but to me, I would like to have more bass response. My budget would be $100-150 for a pair. Any help would be greatly appreciated.