I'm upgrading from an RCA HTIB receiver which came with an unpowered subwoofer, and I'm wondering if there's any way it could be reused with my new receiver. I've had my eyes on the Denon 1707 for awhile now and it looks like exactly what I need for my 5.1 setup and, more importantly, what I can afford at the moment.

But as with all the quality receivers I've seen, it only offers a subwoofer pre out. I'd rather not spend another 200 dollars on a power subwoofer, and I've run both preamplified subwoofer and speaker level cables through the wall. So my question is this:

Is there a way to connect an unpowered subwoofer to any of the speaker level connections on this receiver? I spoke with a salesman about this and he said the best thing I could do would be to connect the subwoofer + and - connections to both back speaker + and - connections. Is this acceptable, or even safe for the receiver?

And if not, is there some sort of amplifier I could put in between my unpowered subwoofer and the pre out? I wouldn't nessicarily be looking for quality, but if there's something that I could use for this, I'd appreciate a recommendation.

Thanks for the help. :D