Anytime Icey! I LOVE giving my opinion.
I wouldn't be surprised if the MKIV either started with 3 channel and later models came with 4 channel or has 4 channel from the start. IF I recall correctly, the MR-2 had 3 channel until '95 or so and then graduated to 4 channel. You might ask Phil in the MKIV section, check out the FAQ there first.