My personal feeling is that the PB13 is a tad better for HT use as it reaches lower than either the EP500 or 600. I like the sound the EP series of subs has with music, very smooth and diffuse, it comes down to personal preferrence.
If your room is small the 500 will work great, it reaches a little lower than the 350 and for HT I have found the extra extension to make for better viewing. If your room is getting toward the larger sizes I would then suggest getting the EP600 or PB13-Ultra. If you can afford it the EP800, based on reveiws by those that have, or heard the PB13 and EP600, offers the best of both of them.
