The ASW610 is a pretty good sub!!! But the XP is in a whole different legue. This sub has only been is stores in the UK for about 3 days, so listening is pretty much out of the question.
Using it with 683`s will sound ACE (thats BIG ACE)!!!!!
You can`t actully hear the bass, you get a really REALLY deep humm, that you can sort of `feel` in your ears.
I would go for the XP for gaming any day. It is the only cheaper sub that you will see effortlessly shaking and flexing to (halo) games. It has to be seen to be believed!!!!!
But if you are looking for a boomier more powerfull bass go for an SVS or a Klipsch.