whats the best choice?

[E150GT]

Well having attended the GTG this weekend and seeing some awesome cars, I started to think about my own. When do you decide if its better to replace the current car, or just keep fixing it up? My current car has a few things that need attending to, and I know its gonna take 3-4 grand on top of what I have already spent to get it there. I saw a 118k 560sec that seemed pretty clean on CL for 5k. I am thinking maybe its better to start with a little nicer car and go from there, as opposed to revamping mine. maybe you guys could help decide?

So far ive replaced the following:
1. rear axles (new)
2. front window regulators
3. flex discs/ctr bearing/diff mount
4. brakes/lines
5. misc stuff here and there
6. new exhaust

Needs attending to:
1. sunroof
2. wheel refinish
3. wood trim refinish
4. dash
5. al seats need re-doing
6. numerous oil leaks
7. real bad driveline slop ( I can hear and feel the driveshaft rocking when the car downshifts coming to a stop and it clunks when shifting up slowly)
8. need small amounts of boywork and needs bumpers with an eventual paintjob
9. front end and all rubber bushings need replacement. car is starting to creak when i turn the steering wheel.

While the parts I have replaced were expenisve, I feel I havent seen anything yet compared to the cost of what I need to do.