For the best handling, I'd get a solid non adjustable bar, or something very close to it. A Neuspeed bar is a good choice since it connects both towers at 4 points and is a solid peice. A Type-R replica can also work.

Adjustable bars [bars with those round things towards the ends] tend to flex under hard cornering. Which can possibly break the bar. The bar can also move up and down at the connecting points.