cage depends on why you are putting it in, are you building a spec track car to run in a series or for added personal safety?
I have seen some cages that are bolt in and offer more safety for lapping, but would not pass tech for race series. so many options out there, if you want to keep the sunroof a removable bolt in cage would problley be the way to go. on the other hand, not many people buying a track car worry about a sunroof, so loosing it will reduce weight.
full cage will not be legal to drive on the street, so a bolt in with removable front bars is the only way to keep it without trailering it too, option is a hitch with a small utility trailer to bring track rims, gas cans, jack, tools ect
as for car worth, yes it all depends on market and buyer