I second the EL34 recommendation. I have a Cary V12R with my 988s that really mske the music palpable/holographic. I have never felt the need to crank the volume on my preamp past the 10:00 to 11:00 position. I also tried a Dynaco ST-70 that worked well too, though the bass was a bit mushier. My room size is 15x13. YMMV.
