The 750 is an implementation of a design provided by Nelson Pass, similar in architecture to the Aleph P. Due to these budget constraints it can't compare favorably in performance to the exquisite design and parts quality of the P, especially in active mode, but it's known to be quite decent in passive mode. Back when I needed to make the decision as to how to drive my Aleph 2s the choice was a new(ish) 750 for $1000-1200 or a used Aleph P (orig $4k) for $1800. Getting the Aleph was a no-brainer. Now that 750s are about $700 there may be some value there. Can't help you on the Quad. Good Luck.