I always liked my Acute with the original JJs, but I bought a pair of 6DJ8 Amperex Bugle Boys from Andy at Vintage Tube Services in 2012 and they sound just great, IMO. Full-bodied, detailed, not harsh. I've seen no reason to fool around with other tubes since then. They were a bit expensive, $266 for the pair shipped, but well worth it, IMO.