Yep. 5 years ago when I got rid of the Turbo GT, I was just sick of the money, time, and the amount of time it was broke. I think I would have been happy with the Kenne Bell Mach 1, but it broke as well. The 69 filled in the gap this past year for me, but I am loosing interest in it as well. I've been to the track like 3 times in 5 years and I was religious about going every week. Just not that interested anymore. Still like reading, taking about cars lol.
As far as what they are worth, prepare yourself for disappointment and a fraction of what you have put into them. Being as you have 2 toys, Id either get rid of both and get something else, or just keep one of them and solider through it.