My second system with JBL 4301b monitors gets a lot of listening time and I'v switched a number of amps/preamps in and out of the system and finally can say that the 4301B now sound the best I'v ever heard them after settling on a Threshold SA/3 amp (class a / 50 watts x 2) and a SL10 preamp (with MC & MM phono). The detail/accuracy of the sound is now noticably better than when used with any prior amps/preamps. The Threshold units were updated by Jon Soderberg who formerly worked with Nelson Pass at the original Threshold Corp. Both are roughly 25 years old and needed to have the caps changed out and monor service. If any member here is looking to upgrade I can highly recommend vintage Threshold equipment and if it is ready due to age for service Jon Soderberg is a highly capable person to do the service at a reasonable price. The Threshold amps were built with the best available components/materials at the time and with service will last a lifetime. About the only possible area for improvement for me is the speakers themselves. I have read a post where Zilch rebuilt the 4301b crossovers for a LH member and the end results were excellent according to the member. Once things settle down the crossovers will be on the way to Zilch for him to update the caps etc. It might be preaching to the chior to say here that almost any of the pro and totl home JBL speakers matched with excellent electronics are hard to beat.