I have the 909, never heard the 99. All I can tell you is this amp has a beautiful midrange, a grainless top end and never sounds strained. Reveiwers seem to prefer the 909. Dont know what led me to the Quad, but Im very happy with it. One note: mine took at least a month to 'burn in'. I know some dont believe in this, but this was my experience while comparing it to an other good amp. The bass was suspect at first, now it sounds excellent.
