I have owned the Stratus Gold i's for approximately a year and a half. Haven't heard them with the B&K 4420, but have had considerable in home experience in conjunction with the following amps: Bryston 3B, 3BST, 4BST, McCormack DNA-1, Houston GSP-02, VAC VT-100 MK II monoblocks AND the Belles 150, 150A Hot Rod, Andy Bartha modified Belles 150 A. Without getting into detail, though I absolutely love the Bryston products in general, my experience as far as the Golds are concerned is that of all the solid states, the BEST synergy by far was evidenced in conjunction with the Belles amps. The Bartha modified unit offers the most excellent low frequency response, but it is of course an after-market modification and I don't know if you'd want to go that route. Other than that, the stock Hot Rod reigns supreme---clearly a cut above the "basic" 150A unit which as I have said, was itself better than all others of the above solid state amps. Hope this helps. Good luck!