Jickie, as of right now I'm not running a center...but I plan to. I just haven't gotten around to ordering one. I just went through a system overhaul and that's the next thing on the list. AV123 is about to release the matching center for x-ls, called the x-cs. You can find pics and some info on it
here. I was waiting on this to come out to see its size to see if it would work for me. It's too big, so I'm going to order a single x-ls, and run 3 x-ls speakers across the front.
The bass is substantial in the x-ls. I run them without sub (for music) almost exclusively due to my apartment-life situation, but have used my sub from time to time. Again, for music that may be fine, but if you're looking to get good HT performance, you'll want to add a sub. With that said, these will work well for you until you get around to getting a sub. They use 6.5" drivers and are rated down to 55Hz. While that isn't all that low, they'll probably seem to go lower once you have them in room.