6922 tube question

I have a preamp which uses two 6922 tubes, currently Sovtek. To my ears, the sound is overly warm and the bottom end sounds bloated. I'm wondering if anyone can suggest a tube, 6922 or otherwise, that will clean up the sound.

I'd like a crisper, more neutral sound while maintaining strong lows (though not bloated) and extended highs. Any thoughts are highly appreciated.

Also, how long is recommended for tube break-in?