A zillion answers on the Bottlehead Forum but you're here, so what the heck. My experience with the 'Mours is that given the C4S, the output caps are #1 and Auricaps were great followed by Clarity. Surpriisng, the little coupling cap was a noticeable upgrade as well even tho an afterthought and all I did was replace the ceramic with a Solen. Based on my experience with adding a choke to Ella, I think the BC-15 choke upgrade will be VERY good, replacing the whatchacallit resitor with the stock choke. After all that, I feel that that the S.E.T. crowd is kidding itself with all this "palpable presence" stuff. These little designs roll off the treble and smear the mids so wacky speakers like Fostex and their ilk don't sound so bad. Gimme 40 or 60 Manly Push Pull EL-34 watts as G-D and Williamson intended!