Go for a fitting. If you have any doubts about your irons play, stay away from the MB. While they are fantastic irons (they are in my bag!), they offer no forgiveness. If you miss hit them, you will no doubt end up with a pretty poor shot.

The CB is a lot more forgiving and gives the ability to shape your shots.

You may end up with AP2s in the longer irons and CBs in the short.

Your fitter will be your best advisor.

Rationally, do not look beyond AP2. Jordan Speith plays AP2. Do you need more feedback or less offset or better feel than him? On the other hand, if you truly love CB or MB look (or looks of other people to your bag) or feel and that would make you happier golfer, or very very surprisingly a fitting would show CB or MB are better fit for you, then go on for that...
Otherwise, as a 7HCP you should be OK to handle AP2, certainly short and mid irons. Long irons consider AP1, AP3 or TMb or hybrids. Spieth plays TMB as long irons, not AP2.

Peter, as a side note, I did a pretty extensive fitting about a month ago and I was pretty sure that I would end up with the AP3/AP2 combo. However, the absolute best numbers that I got were from the MB. I have been playing them for years and thought it might be time for a change but the numbers just don't lie.

I agree with the AP2 recommendation, I went through a full fitting of a every 718 iron as I was looking to make a purchase. I also play at a 7 and I found the MB and CB to be much less forgiving, I would have to practice more to play them. I dont work the ball too much so I eventually decided on the AP 1. My results suggested anything less than the ap1 were not as accurate, its a personal preference at the end of the day but unless you want a smaller clubhead, or the ability to work the ball you might find the ap1's to be the most accurate. I played the new ap1's yesterday and they are amazingly forgiving and feel great to hit.