When I had the 988's, I tried a number of amps: EAR 509ii's (509 tube), Wolcott Stereo-220 (EL34), Quicksilver Triodes (6C33C), Cary SLM-100 (EL34/KT88/6550), Cary SLM-70 (EL34/KT88/6550), Odyssey Stratos Dual Mono, Aragon 2004, and I can't remember how many others! For the tubes, I ended up keeping the SLM-70's. They were modified to be switchable b/t triode and pentode. They had the nicest tonal balance and inner detail of all the tube amps listed. (Disclosure - I am soon to list these on Agon, as I sold the Quads a couple years ago.) A real sleeper with the 988's was the Aragon. It didn't have quite the beautiful mids and tonal balance of the Cary's, but it had great dynamic drive and spatial resolution. For $1200 it makes a great summer amp, or backup amp!
One other peice of advise on the 988's. They are not the most dynamic speakers, so you want to have really dynamic gear upstream. Swapping my Audible Illusions 3a preamp for a Cat Ultimate brought a great improvement. Also, good power cords on the speakers made an audible improvement (I made DIY cords based on a Chris VanHaus design). I also liked raising the speakers by about 10" on solid wood blocks (big beams cut 26" long) to improve the imaging - any higher yielded too much loss in bass.
Best, Peter
One other peice of advise on the 988's. They are not the most dynamic speakers, so you want to have really dynamic gear upstream. Swapping my Audible Illusions 3a preamp for a Cat Ultimate brought a great improvement. Also, good power cords on the speakers made an audible improvement (I made DIY cords based on a Chris VanHaus design). I also liked raising the speakers by about 10" on solid wood blocks (big beams cut 26" long) to improve the imaging - any higher yielded too much loss in bass.
Best, Peter