I owned a Cronus Magnum II and liked it. However, I always felt that the sound signature leaned a little towards SS for my taste. I sold it to another gentleman who had it upgraded to Cronus Magnum III and told me that it was substantially better. If you like the overall sound of your Magnum II, it's worth checking with Rogue Audio first.
It will help if you can specify your budget and whether you're open to buying used.