Do you know for a fact that the IAC is bad ? I would clean it out with some throttle body cleaner first, and if that doesn't work go to the junkyard for 5 bucks, then clean that one. As far as if your going to get a new one I would stick with OEM. I like aftermarket parts (It's no secret) but this valve is responsible for Idle and coasting idle so it's kind of important.
I installed (long time ago) one BWD from AAP store and it works perfectly. This is not a part that requries a super technology to be produced, so IMO third-party is OK
Sure, nothing beats the junkyard prices, but... there is no guarantee that will be working for a long time.
The aftermarket ones do not hold up well, and the precision need is very strict. Many aftermarket ones act like an OE one that is starting to stick. OE is th best route, they last longer, and work right the first time. That being said, Delphi is an OE manufacturer, their part should be excellent.