You will not find better speakers than the Behringer B2030P for the price. Among all of the speakers currently available, these have verified measured performance relevant to human perception that vastly out classes anything else anywhere near their price. Their build/parts quality also is far above anything else in this price class, which is to be expected, given their high performance level. You can buy 3 pairs and have enough for a 6.1 system, and couple them with a subwoofer or two. This does go over your intended budget, but you are getting very good speakers, and you will have no reason to upgrade them for a very long time. You can further improve the fidelity by doing some very simple/cheap modifications to the speakers.
-Chris