You need to research the cage rules about the type of racing you will be doing initially, and any kind of racing you realistically forsee yourself doing in the future.
Reason I say this is because you:
A) Do not want to pay for a cage that you put in and won't pass tech for the racing that you want to do now, then have to spend the money again.
B) Do not want to put a cage in that passes tech for the type of racing you are doing now, but be SOL in the future when you want to step it up.
Both issues lead to you spending more money. But this is why I say do it all now.
Cage welding is not easy, trust me, I've done it and continue to do it. It is awkward, tight, and systematic. That's BEFORE you are trying to make a bolt in cage into a full Honda Challenge car. Once you have a cage in the car it is very difficult to make modifications or change things. It takes a lot of extra time, and a lot of extra money out of your pocket.
The other reason that custom cages are better than the premade ones, is not due to fit and finish necessarily, but because sometimes they are just as expensive to weld in as a premade is. Why? Because of the fitment. Premade ones aren't guaranteed to fit, and TIG welding needs precise fitment to not only look nice, but even be possible. Premades don't always fit nice, so instead the cage builder has to sit there and tweak and move and modify bars all over the place. After which, what didn't really fit then definitely doesn't fit now, and it's all a mess.
What I'm saying, spend the money and put a well made cage in the car that will cover you for any class you want to run. You will save money and aggravation in the long run. Trust me, I know, I have to convert my 6pt into a 10pt and it is going to be a nightmare. :fuuu: