I have the 9632, and after upgrading my pc I could not use it for the same reason. No PCI slot. I researched the adaptors solution, but after reading some horror stories about chips frying, compatibility issues with the 9632, and potentially using an adaptor being a bet, I decided to get a Digiface USB ! And am I glad, I did!! And it costs almost as much as the 9632, new!
So what Ramses suggested is a better route to take, or if you already have external converters(with ADAT In/Out) you can consider the Digiface USB, for not breaking the bank. It has 4 ADAT Ins and Outs, which can also be set as SPDIF(depends on what you need), plus a headphones Out. And the RME drivers are the best in my experience!
If you elaborate a bit more about your setup, we can come up with more ideas!
Of course, I kept the 9632 as a backup solution, but have not yet built my backup pc.
RME Gear: Digiface USB, HDSP 9632