Me too!... somewhat
I am going to be building a Zep with Chorus soon! I ride Ultegra and also campy mirage mixed with some Shimano stuff. What I can tell you is that if you want Swiss watch.. definitely go with Campy like the other guy said. If you want Casio, then go with Shimano. No offence as I think Casios are great watches too. The feel of Campy is more precise but in terms of performance I would still rate Ultegra over Centaur. I think Ultegras are closer to Chorus, but a little lower.
Ultegra I think is a little lighter than Centaur, I personally would just bite the bullet and go with Chorus, the difference in weight, reliability and durability is too great I think. However, seeing that you are on a budget, I recommend that you either just change the shifters and rear D for Chorus (if you are ordering from Airborne as a complete bike). That way your bike will feel like a Chorus run machine without adding too much. Then make it up somewhere else like perhaps a cheaper stem+bar combo. However, if you are more concerned with weight, then go with Ultegra instead of Centaur.
Or you could always go with a Zep instead of MP because they are essentially the same except for the carbon stays which I think are market hype anyways.
I would recommend another pair of wheels but then you probably have them from another bike or have a good deal or really really like them.
regards,
Sean