If you replace your high end PC with a Mac, I would rather go with a 4 to 6 pin firewire cable (I get mine from the same place regfran suggests) than a firewire expresscard adapter for a couple of reasons;
- Firewire is on it's way out and driver support will surely follow for 3rd party cards (expresscards)
- I've found the expresscards to be expensive and the locking mechanism to be flimsy
Simplify your future troubleshooting, just get a couple cables.
-N