All right! The XS15 is set up and tuned to my preferences now and I LOVE IT. I'm not going into great detail of my initial impressions, as I'm still enjoying this amazing sub while I write this, but this is more of my first reaction to SQ and quality. It's BIG. Bigger than what I was hoping for. But, it's manageable within my space, which is good. It fits snugly into the far corner of the room, so I'm happy with that.
Now, on to the music listening. I'm not doing something right in regards to music listening. I put in a few cd's into my trusty Oppo, and while the lower frequencies are cleaner, the dynamic range isn't quite where I would have expected it to be. I read somewhere that if the sub is connected via LFE, music listening won't represent accurately....or maybe I'm just not remembering correctly. Either way, I don't feel music is as dynamic as it should be. I used Pearl Jam, Daft Punk and some other bassy tracks. It sounded good, but not what I was hoping for. I don't listen to music in my HT much, so it's not really an issue. I'll revisit that late rthough.
Now, movie watching is a whole different story with the XS15.
I popped in The Hulk and skipped to the sonic boom scene. Wowzers. The lower frequencies seriously knocked my socks off. The fart canon blasts have been replaced with a nice, clean and confident thump, boom and blam (for the lack of better words). Everything sounds the way I had imagined it. The dynamic range that I have been missing kicks in overdrive when action scene passages occur. I'm really happy with the results of my XS15. My small theater room needed this added range and clarity in the bass department, and I'm absolutely loving it. Fiance, not so much. I haven't fiddled much with placement, since I'm a bit limited on space, but I think it's working great where it is now.
I have the crossover set to 90hz, which seems to be the sweet spot to my ears. I'm getting a new Pioneer 1222 in this Friday, as my Onkyo NR509 is a bit behind the capacity of my speakers. Also, I hear the Pioneer has great SQ and driving capabilities. I'm loving everything about my new XS15 so far, and can't wait to push it more with my Blu Ray collection. I'm extremely happy with this purchase.
More photos and some shots of my humble little theater room

. Thanks to all of you for your suggestions! I think I've found a real winner in the subwoofer department.