I'm not familiar with those things, but my instincts are that you should probably stick with speakers that are very easy to drive. The unit may even specify a recommended speaker rating on the back.

If you could locate a user manual, either on the web or simply post the information in this thread we could probably help.

Unless someone here just happens to be familiar with that thing, we would simply be guessing.

The biggest problem you have is this is a large space to fill and I would recommend staying with 2-channel if you can. You are going to need something closer to PA quality than hi-fi due to the size of the room and your budget.

$500 is not quite going to do it I am afraid.
B215

A pair of these would fill your room and they have built in amps so you could drive them with a sound card and control the output/volume with the computer audio program. The 15" speaker would fill your large space adequately. It is not high end audio, but I think it would meet your needs. They are $500 a pair.

You could use the tone controls of your sound card/audio software to try and match the speakers to the room, whether too bright or too highly damped. I am asuming it is mostly hard surfaces and no carpet.

The B212's are the same with a 12" woofer and less bass output, but would be $100 less a pair at $400.00 . This would leave you $100 for a sound card.
B212

Good thinking, Jim.

I can recommend the Roland CM-30 Cube Monitor. They have excellent sound for an inexpensive self-powered PA speaker. A couple of these will fill a very good sized room with no problem. http://www.musiciansfriend.com/product/Roland-CM30-Cube-Monitor?sku=608895