I understand you are going to upgrade your turntable, but you didn't mention if you are going to keep the Dynavector 507 MK II.
The XV-1S is a cartridge I have longed for, simply can't afford it, but I'd love to have one. I'm using an earlier DV 501 arm with a Soundsmith-retipped XX2MKII on a Garrard 401. Phono preamp is a Modwright SWP 9.0 SE, with upgraded power supply.
So, I have an inkling of what your analog front end sounds like, therefore I know you are enjoying some very special listening sessions.
Enjoy your new Maggie 20.7's, and congrats on a fine system.
Regards,
Dan