Hi @Martin Vigesaa If you can I would get a TI chip-set Firewire card. Focusrite have always been very specific about using TI chip-set. I have used two Focusrite Saffire firewire interfaces, my first was an older 26 I/O that was under 32 OS and currently I also use a Pro 40 over 3 different PC's always with a TI (Texas Instruments) Firewire card and I have never had an issue with either of the interfaces.
I found Startech cards to be very good, I had one go bad after 23 months they replaced it within 48 hrs.
Functionally I am running my Pro 40 with the Firewire Latency set to Small, and a ASIO buffer of 128 samples with a total round trip time of 7.9 msec's glitch free. Most of the music I make is with Arturia's modelling synths which can be quite CPU heavy.