If it is the series 1, I think they are pretty nice, especially for the money. I've use them as front L & R that I have paired with an HTM61.
$500 for the two 684's is a decent deal.
My only complaint is the mids can be a little forward, but I've been happy with them. You will need a sub as the low end is alright - just not quite enough, at least within my setup.
Edit: detail.