Nagaoka MP500 is MI??? I always thought of Nagaoka cartridges as MM types.
I went to the Grado site to read about the Epoch3. It seems like a high premium to pay vs their slightly lesser products for cocobolo wood case, gold coils, a sapphire cantilever, and a stylus shape that they are a bit mysterious in describing but might be elliptical. For about one-third the price, you can have jarrah wood and a boron cantilever (the Statement3). However, the proof of the pudding is in the music each cartridge makes.
Hope RV does not mind us playing on his thread.