in my opinion, I think the the Neumann's need a cleaner pre-amp to really sound good.
I started off with a pair of AKG 391's, running them through a ps2 > ad20. then I sold the ad20, and bought some line transformers and a modSBM-1. I thought the modSBM1 was great with the AKG's, but then I sold the 391's and bought a pair of km184's. I thought that this combo really wasn't a good match. so, I started thinking about picking up a used V2. but with then decided to sell the modSBM1 instead and bought a new V3. Granted, this isn't with an mp-2. however, I think as a general statement, both the mp-2 and the modSBM1 can be described as "colored" or "warm" or whatever. the point that I'm trying to make is that, IMO, you'd be much happier running a very clean pre-amp with the Neumann's. and IMO, the mp-2 is not the cleanest of pre-amps.
to sum up, I think the km184's are great mics. I definitely think they are a step up from the bluelines. but, if you decide to go for it, perhaps also consider selling the mp-2. oh, and km184 vs. mbho's. I'd definitely pick the km184 over the ho's. with the km184, you get the smooth classic neumann sound. with the MBHO's, you don't.
of course, the with the km184's, you are "limited" to card's, but you've probably already considered that (and I put "limited" in quotes, because I think 80-90% of the time, I'd be running cards anyway.)