Yeah, I think hearing the best OTS header would help you determine if it is more that specific header, or any aftermarket header in general that is responsible for the sound you are hearing. From what I've heard though, the PLM header is notorious for having excessively loud header hiss.
I'm interested to hear your FR exhaust, as well as check out your BRIDE shift boot.
Regarding the Skunk2 header, I got it for $525 shipped to my door and it included the OEM O2 extender. If you can get one of the O2 extenders, then I would say get a Skunk2 header. Hell, you can get an Alpha header for $385 shipped brand new for Autocity Imports, and Skunk2 says that it uses the same thickness tubing as well as design of the Megapower, just a different welding and back-purging process.
If you can't get an OEM O2 extender, then I would definitely go with an Invidia header. You can get a good deal on a used one, and you don't have to extend anything. Simply bolt it up and you're good to go.