Keep in mind that, as with all Firewire interfaces, there are serious latency issues that may affect the way you work.
Firewire is great in those circumstances where a PCI card isn't possible -- and it's got plenty of throughput so you can run multitrack material that wouldn't be possible with, say, a USB (1.1) interface -- but because the standard [Firewire] buffer size is large and takes a while to fill up, a dedicated PCI card interface will deliver much lower roundtrip latency times.
Hotshot chip designer Joe Bryan of Universal Audio recently wrote, “Most ADCs and DACs have only about 27 to 34 samples of delay in their internal digital (downsampling) filters, plus a few samples in the hardware interfaces. That means the total A/D/A delay is around 64 samples, or 1.33 ms at 48 kHz, not 1.5 ms for each A/D or D/A conversion...”
However, FireWire “transfers data every 125 microseconds, but the hardware actually has significantly larger buffers, and the ‘standard’ AM824 protocol [used in mLAN and other implementations] is moving towards using several hundred samples of buffering to overcome multidevice bridging and merging issues.
These delays are unacceptable in professional audio applications, so there is still a need for a low-cost, low-latency, multichannel, digital audio transport.” Bryan says he's working to form an industry group to create a better transport standard.
[Quoted in October Electronic Musician Letters Column
http://emusician.com/ar/emusic_letters_27/index.htm ]
However, you can mitigate the problem somewhat by making use of the "zero-latency" monitoring now built into many of the newer outboard interfaces. This is no miracle, despite some of the ridiculous and sometimes misleading hype you will see, however. It simply means that there is a "headphone mix" type output before the initial A-to-D conversion. Some devices actually add some rudimentary reverb or other effects to this mix to get over many singer's objections to hearing their voices 'dry' in the monitor. [Interestingly, the lowly SoundBlaster has had this zero latency monitoring functionality for years. But you'd think from some company's hype that this was some great new advance. The great new advance is that some of the first generation of USB and Firewire devices didn't have this sensible and predictably desirable feature and early adopters screamed like stuck pigs when they confronted the latency issues of their new devices.]