just be aware that the arm & cartridge need to be compatible, regarding cartrige compliance & effective arm mass. I dunno those spec's for either your Dyna or JMW so you'll need to find out. When you do get that information then refer to this link, which has the info. that you'll need to find out if in fact you have that compatibility factor:
http://www.gcaudio.com/Archives/tonearmcartidge.htm
Also, do browse around the analog corner archives while you're there; you'll learn alot:
http://www.gcaudio.com/Archives/gcaarchives.html
I also have a MK-IV with the aforementioned bearing/platter upgrades. FYI: I have the Grado Signature arm (medium mass) with the Grado Statement Reference {the 0.5mV low output model} (medium compliance) which is an excellent sounding combo. If you're willing to $pend at that level (apparently so) you would probably need the high output model though, or at least the medium one due to your low-ish phono gain. Yes the lower output models do offer better transparency, but as you say, the required step-up transformer might negate that benefit. I've seen these $1200 list Grado's available for around $800 new. These Grado's are not moving coils, nor are they moving magnets. They're variable-reluctance moving-iron designs, which combine the benefit of m.c.'s low cantilever mass without some of the other drawbacks of either moving coil or moving magnet architectures.
http://www.gcaudio.com/Archives/tonearmcartidge.htm
Also, do browse around the analog corner archives while you're there; you'll learn alot:
http://www.gcaudio.com/Archives/gcaarchives.html
I also have a MK-IV with the aforementioned bearing/platter upgrades. FYI: I have the Grado Signature arm (medium mass) with the Grado Statement Reference {the 0.5mV low output model} (medium compliance) which is an excellent sounding combo. If you're willing to $pend at that level (apparently so) you would probably need the high output model though, or at least the medium one due to your low-ish phono gain. Yes the lower output models do offer better transparency, but as you say, the required step-up transformer might negate that benefit. I've seen these $1200 list Grado's available for around $800 new. These Grado's are not moving coils, nor are they moving magnets. They're variable-reluctance moving-iron designs, which combine the benefit of m.c.'s low cantilever mass without some of the other drawbacks of either moving coil or moving magnet architectures.