Can you explain exactly why you think it wouldnt work , even if a poster before had good experiences with HP pavilion and USB interface ---why DO you say it would not work (or 2%) with a Texas Instruments express card ----you just know ???? How do you explain that - 4 real ARE YOU JUST MAKING COMMERCIAL for your kentucky fried stuff??? It sure sounds like it...LOL 4 ultra real now....
I'm not Scott... but I know the answer to your question

The reason why you can't simply use a cardbus/expresscard TI chipset controller is actually very simple:
The cardbus/expresscard controller in these units is also "crap"... so you're not circumventing the original problem.
Firewire works great with a laptop *if* it has a good onboard TI chipset controller.
BTW, Even if you could use a TI chipset expresscard controller, it's still not ideal.
For maximum performance, you want to save that slot for an eSATA controller.
A laptop with good onboard TI chipset Firewire... recording to a fast eSATA HD is as good as it gets.
Of course... this isn't a cheap/inexpensive option.
This is strickly my opinion, but if you have high performance expectations, I don't think a laptop any less than an Aluminum Macbook Pro is worth having. Anything less is extremely slow when compared to current tower systems...
It's all too easy to spend $1200-$1500...and wind up with a mobile DAW that's totally sub-par.
Make sure you do your homework before you pull the trigger.