Amp upgrade
Those B&Ws should be a nice upgrade, even with your current receiver. Their 8 ohm load is not perticularly difficult to drive, but if you have a huge room, and play it really loud then you might find your receiver lacking.
If you want to experiment with an amp upgrade for the mains, check out the Behringer A500 for $180. Rotel builds great amps, but one of the Mid-Fi Denon receivers like the 3806 should have comparable 2-channel power ratings and a better pre-amp stage than your current one.