I did a combo set of 3-7 in the CB an 8-PW in the MB.
Shafted them up and have a few round on them (not a lot since I do monthly tournaments and don't want to change without enough practice).
I have not seen much difference in distance from my Nike 2012 VR Pro Cavity irons except on the occasional shot that goes 10-15 yards further.
I actually prefer the feel of the MB heads to the CB, but didn't want to attempt a 4 in the MB (I don't think they have a 3).
I don't care for the look of the faces as they seem like they will look beat-up after only 20 rounds (I keep my irons a while).