I want to swap out the Tungsol 5881's in my Super (yeah I know they cant handle the plate voltage. ) I just got the amp and want some good NOS not current production 6L6GC's or 7581A's. There are so many tube choices out there I cant decide what to get for BIG bottom end and a smooth creamy breakup. The last tubes I tried were the tall bottle Sylvania 6L6GC's and the tube change before that - Philips ECG 6L6GC's. Here's what Ive narrowed my choices down to: Sylvania STR-387 Philips 7581A's GE 7581A's (pink base) BFSR owners, which american glass would you choose?