This is a system I have accumulated over the last year having changed from an audio research based system which I enjoyed for many years to an art audio based system the focus point of which is the diavolo amp. I replaced my hales speakers with the Tetra 506 lmtd these speakers were the ones reviewed in the online magazine tone and took this system to another level. At this point I listen primarily to vinyl and at some point will probably upgrade my tt. Any advice or input is certainly welcome!
I am a confessed dipole fanatic so I have a weak spot for Magnepans. Maggie 3.6R (even the 1.6QR, but it sounds like you are aiming higher than that!) would be a classic match for your ARC front end (ARC and Magnepan were joined at the hip at birth). Maggies are not particularly famed for their dynamics but the latest generation are said to be improved in that regard. The Vandersteen 2WQ subwoofer (2 are said to be better still!) mates well with the Maggies for even better dynamics. I find that Von Schweikerts image in a far more forward fashion(in your face, basically) while Maggies, like most planars, image from the speaker back towards the front wall and beyond. Depends on what you like.