I hear you...its amazing how expensive things get the bigger you go!
The XP series are "OK" in my opinion. Like I said, I have one, but it doesn't seem to be as effective as the Magnum 350 it replaced (which is about 1/2 the cost). It seems that people that have XPs either love 'em or hate 'em. I am more like "blah" with it. Since you are looking more towards "extra filtration"...you may even want to check out the 350.
One nice thing about the XPs, you can pretty much configure the baskets how you want. You can make them all mechanical and use either expensive filter pads or make your own from floss. You can use bio balls, stars, etc for bio filtration or use filter socks and toss in some carbon if need be. Of course with 3 baskets (XP3) or 4 (XP4), you can also configure combinations of the different filter processes.
Since your tank is already advanced, I suggest you look at another canister versus the 110. It's a damn good filter, but I think you are beyond it already.
Good luck!