Site is work in progress, tryin to decide what to put on it and all.
MOTU has a great rep on Mac's, and rightfully so- their software line revolves around Digital Performer, Mac only.
Are you using Cakewalk or Sonor? There may be some better choices for an audio interface then, since you are using Win XP. For instance: Alot of people using Cubase or Nuendo on PC have found the RME line of cards to be better for them, simply because the ASIO drivers (gets the audio in and out) allow extremely low latency, as low as 1.5 milliseconds.
Another question is: Will you be looking for a portable solution? One you can use with say a laptop? Or will you simply want it for your own persnal, home use? Number of inputs and outputs you would like also will play a part. I'm sure there are forums where people using the same software you currently use hang out, and they would have idscussed "best hardware to use" a hundred times or so. How much you are looking to spend, does midi need to be part of the same unit, does it need to be portable? Also, beware that many PC's with "onboard" firewire are not 100% reliable when used with some of the available Firewire audio interfaces. Although a PCI Firewire card is easy to find and install, and is relatively cheap, it is somtething else to keep in mind.
Sounds daunting, but I have found that a good week's worth of research can save a month's worth of headaches
I would do a search for forums specifically dealing with your software, and see what they are using. These days, most manufactures (in your case Cakewalk) have some sort of forums on or linked from their main site. Feel free to keep throwing out questions, if I can help, I will
edit: just did a quickie search. Seems Cakewalk decided to go with a different route: They have a set of Newsgroups, set up like most forums.
They look decent, and looks like there are different groups for different software available from Cakewalk.