Hmm, the GTX Is quite a large card, considering the case is meant to be a Mid-ATX That's pretty good. I Still havn't quite chosen my new case so im kinda looking around for ideas....
Unfortunately it's really hard to space out a case in advance for liquid cooling. The best thing you can do is to Google P183 liquid cooling on images and see if anyone else has attempted/succeeded/liked it.
Here's one from Xtremesystems with an Exos drop in.
And another with an internal setup. The user says it's a bit crowded. It doesn't help that he is using way over-sized tubing.
Updated pics since I moved into my apartment. These are actually older pics. But the only thing that's changed is I found a way to raise the surround speakers by the couch. The HTPC was mainly for Netflix and online videos, but I tend to use it more now because the couch is comfortable.