Don't sweat the matched vs unmatched dilemma. Schoeps manufacturing is close tolerance. (I even have a Nextel-grey MK8 capsule that matches well acoustically with a chrome-cased MK8 that I picked up a year later.)
The MK5 is good value. A colleague's MK5 - that he bought as a matched pair for a small additional charge - sounds in cardioid mode much the same as my MK4, and in omni mode, pretty close to my MK2S. I have no experience, though, about deploying them in rock concert venues.