Soundcard: PC vs USB for laptop? 16 vs 24 bit for REW and more?

[tweakophyte]

Hi-

Now that I've got my Galaxy 140 in hand I am "upgrading" my work laptop for some more fun.
...my dumb questions...

I noticed a lot of people with laptops use an external, USB soundcard instead of a PC card. Why?

I also noticed that many people are happy with a 16-bit soundcard (like SBLive MP3+) versus a 24-bit version. I'll be using REW for sub eq-ing for now. In the future I'd like to measure the whole audio spectrum and maybe get into some of the other measurement sw packages (you know how this hobby grows ). What is 16-bit "good enough" for and where would I start wishing I had a 24-bit card?

Any other nice-to-have things I should consider?

Note, the laptop would only be used for testing/measuring, so no HTPC features needed from a soundcard.

Thanks,

[tweakophyte]

No comments? Is cheap the best way to go?

[JohnM]

External USB cards are often used with laptops because many laptops don't have line inputs. 16-bit cards are good enough for anything you may wish to do measurement-wise, REW itself only uses a 16-bit interface to the card so there's no benefit from a 24-bit card with REW.

[tweakophyte]

Perfect.... creative refurb, here I come.

[tweakophyte]

By the way, the refurb SBLive MP3+ USB is about $23 shipped at Creative.com