Hey-Hey!!!,
Thee should be no big suprise that a good PS is the heart of a good amp. I just got done putting some Russian Teflon caps in my amp and linestage. A single .056 uF/500B unit bypassing the main PS cap. It sounds better to me.these things are available for ~$2 each from Gintaras of KWTubes on ebay. Like 6 for $12 plus shipping. So maybe it ought to be called the $3 tweak. Either way, these caps are nice enough I recomend getting a stash for your parts box. They are too useful not to have laying about, and they won't be around forever.
They are about the size of a third of a Hot-Dog, and are TFE sheet and Al foil...
regards,
Douglas