I didnt read everything else, but I've been in your shoes so I'm speaking from experience here. Obviously I dont know much about your finances, but heres my .02.....
If you are squared away financially, (little to no debt, not saving for a house, things like that) and you have the money to "treat" yourself to something else....seriously consider it. 4 years ago I bought a supercharged Bullitt in pristine condition, and I loved the hell out of it for about 2 years. Then around the time I turned 25, life happened and I found myself in tough times. All of a sudden racing/modding/detailing my car didn't seem all that important anymore. Fast forward a couple years, I'm back on my feet, doing pretty well for myself to the point where I can afford to throw money at my Bullitt....but I just don't want to. I've been down that road, I know where it winds up (me a few hundred $ in the hole and the car 0.08 seconds faster than it was last week).
I needed something a little more practical for a DD, so I bought a CSRT-4

jaw

and once you get past the fact that its an SRT-4, and its ugly as sin, its actually pretty fun to drive, not to mention it's convenient as hell having all that room for my dog and hockey equipment. I also ended up buying a bike to satisfy my go-fast needs, and honestly haven't missed the mustang all that much at all....until recently
Long story short, a man needs variety. We get bored easily. If you have all your ducks in a row, and you're not saving the money for retirement....look around. Find something NEW, mustang of not!