OK, I've made some significant changes for now. I decided that I'm not going to get a new monitor until natively 120/144Hz monitors become available in resolutions above 1920x1080 (unless I decide to get an Overlord monitor, but I've got to do some serious research on those before going that route). Hopefully, manufacturers are working on this already, but I might have to wait a while.
Along those same lines, I'm going to get a GTX 780, rather than the next-gen Titan equivalent - I won't need a Titan for gaming on a 60Hz, 1920x1200 monitor. If I get a larger monitor and need more power, I'll simply sell the GTX 780 and get the more powerful one.
So, there we go; it's now officially a ≈$2,500 gaming rig Still, I'm happy with these changes, and now I can save the $1,000 for the upgrades I really want a year or two down the road.