A ping-pong amplifier with reduced glitching is described. The user experience in performing shopping functions is simplified and enhanced over existing methods. An intermediate pulley system is provided that includes a pair of intermediate bar pulleys carried by the upper bar, and an intermediate wall element carrying an intermediate element pulley arranged to be positioned between the first and second end wall elements. The compartment at the front end of the chassis forms first and second corners. The adapter stent and the replacement valve can be mounted on the same catheter for delivery to the implantation site.