Last yr I was looking for a header for my car. Last time I looked at obx they had a header w/ 2 different flex pipes= stick or atx. I haven't seen one like that before. I ended up going w/ a Fwerk's one. You will need a tune so factor that into your budget. I would also recommed a stealth exhaust system. Or a least order the stealth muffler to use w/ your system. For sure go w/ a 2.5'' setup.
I have the Fwerk's header & stealth hooked up to my Borla system.