The MK2 and MK1 in stock form. MK2 hands down sounds better.
The stock MK2 and the Modded MK1 with nickel transformers and VOCM mod. Close. They just sound slightly different. The MK2 has a bigger sound stage. The MK1 seems a little more focused.
I like them both.
MK2 with nickel transformers and the Modded MK1. No question the MK2 wins hands down. Best of both. Larger sound stage and focused with lots of detail.
All above observations were done with the MK2 in default configuration. ( no ground lifts ) and both used a USB shorting plug.