I recommend you run the towers full range and crossover the center and surrounds at 80Hz. If the center is placed in a cabinet, try plugging the ports and using some Auralex Mopads to isolate it from the shelf like I discussed in the review.
If your tweeter is buzzing, have EMP send you a new one or better yet, work out a deal to upgrade to E55tis
The E55tis are a much better speaker IMO and worth the extra $$$.