Well I have had Both as well, My favorite for musicality out of all the thresholds still stands the best valued S150, I like the forte 4a A lot as well but I did not have the Class A' 50 watt version mine was configured in AB, and still very good, I had a s300 as well and the s150 always sounded much better to me, but could be the Synergy situation with certain components and speakers.
Threshold s150 or Forte 4a amplifier?
I have a pair of 4 ohm speakers (2 Peerless High Def 5 1/4 Mid-woofer and Vifa Ring Radiator XT Tweeter in each cabinet) that are around 89 db/ in a fairly small listening room. I have a choice of either the Threshold s150 at 75 watts/channel or the Forte 4a at 50 watts/channel Class A. I am looking for some feed back on both of these amplifiers and suggestions on which amp I should Keep. Thanks in advance for all advise!