From my experience with HT sound formats, e.g., DD 5.1, DTS etc, the speaker quality is NOT very critical. The order of importance is like main speakers > center > sub > surround. I'd put most of the money on the 2 mains if you want to enjoy 2-channel music from the same system.
If you don't mind buying used, I'd highly recommend Dynaudio Contour line, such as 1.1, 1.3mkII, or 1.3SE, they will fit your budget. Dyn speakers are 'drop dead' neutural, uncolored, accurate, and dynamic, build quality second to none. IMHO Dyn makes everything right in speaker design/manufacturing. They fit my philosophy well: hi-fi = high fidelity = truthful to the source. Dyns are extremely revealing but given your B&K it should not be a problem.
Enjoy!
Abe
