If money is no object, I'd get Hytech (if nothing else just to see what it can do on my car)
I personally would not consider CT-E. It is a decent piece, but for me the whole point of modding something on the car is in pursuit of higher level of performance. CT-E doesn't come even close to PLM or WR and costs more, I see no point in that.
PLM, this is an ebay header, functional, good gains, but nothing over WR (I also think that WR is built way better and I don't like long tube headers - PLM - Hytech as they tend to vibrate like tuning forks) and not that much cheaper anyway, also not really possible to install cat with this without cutting cat back, a big NO in my book.
WR is my choice, I have it, I love it, on the car for a while now, massive power for a single mod (all things considered) and it just sings. Short design not prone to vibrating (as much) and really suits the TSX. Bolts up fine, looks good, O2 reaches fine, just route it slightly different, no need for extender. And you can always weld in High Flow cat into provided test pipe. As I said before, they could honestly charge more money for this thing at would be still worth it.
Either way, only real contenders here are PLM and WR. If you are after biggest gains on budget this thread goes a long way to give you details:
http://www.tsxclub.com/forums/1st-gen-engine/51346-plm-header-review.html
Based on your original post I am not sure what your criteria is, so my point of view is based on what I mentioned earlier. If that doesn't apply to you maybe my suggestions are not relevant, but I will say that OBX I wouldn't personally consider under any circumstances given these 4.
Regards,
Nino