Unfortunately, there are essentially no good ready built electronic crossovers on the market for anywhere near $500 or below.

Your only real option, and a very good one at that, is to build one such as this one from Elliot Sound Products, where you can use the Op-Amps, resistors and capacitors of your choice.

24dB Linkwitz-Riley Active Crossover

There are some on the market in your price range, such as one from Behringer , which is an all digital unit, but I'd steer away from these at all costs. For starters, being digital, all analog signals are converted to digital for processing, then converted back to analog. The problem is the question of how good could these converters be for the asking price of the crossover? Not very good, I'd say. Also an unnecessary digital conversion cycle is an extremely high, and totally unacceptable in my view, price to pay for a simple thing like implementing an active crossover.