Soldering isn't the problem, if you have the skills, it's the header itself. What is the orientation of the header and does the card have the lanes for it. Orientation should be solved by finding where the dummy pin is. Good luck finding it with no board labels, though. I've seen USB cards with that VIA chip in all possible orientations, and with various arrangements for the ports. If the card has the lanes connection to it, neat, it means you could try and solder the header, if not, it means they have used a standard base cut-out card and arranged the lanes as they needed. No big surprise.
It's your call, really. If you want to be worry free, go for the one with the 9-pin header already installed, if your that adventurous kind of guy that likes a challenge and have extra pocket money, go for the one that has the holes for the header.