I've always been happy with Certifit. If you have a common vehicle, they have the parts in stock. Prices are excellent, and quality is as good as it gets for non-OEM parts. If you don't have a warehouse nearby though, that's a problem.
I have ordered a bumper, grille, valence, and header panel for my truck off of eBay from a seller with good feedback. I believe the seller was USAutoParts or something to that effect. Shipping was very reasonable, and they sent all the parts via either UPS or FedEx, including the steel front bumper. The parts were from the same Taiwanese suppliers Certifit uses. The fit was spot on, where you notice a difference is in the quality of the materials.
For example, the stock header panel and grille surround on my truck were made of sturdy, thick fiberglass. The Taiwan replacements were made of plastic and were noticeably more flimsy as a result. They work fine if installed with all of the original hardware, but they definitely are not as sturdy as OEM. I have also noticed that metal parts are thinner. Again, not a problem if you use all of the hardware and attachment points, but just not the same as OEM.
So in summary, fit and finish should be fine. Materials will be lesser than OEM quality though.