they are some mighty sizes for a rear bar, evilc has it in a nutshell, and if i went up to those sizes, my car would only be good for a drifting event! also unless they are tubular, the weight will need another 5hp to compensate.
i would go up on rear spring rate and play with tyre preasures/type firstly, then maybe a lighter front bar, i always blanche at adding even a kilo, given that were all doing this to go faster.
