[linux-audio-user] Looking for an external sound card for 'nix -- recommendations?

I've been lurking on LAU for a few months now and I've finally managed to come up with something worth asking: I'm looking for an affordable external sound card for music production. What are your recommendations? Being a novice, I'm having trouble finding what I "need" (and I'm growing wary of google's pagerank system...) so I thought I'd query the real experts. ;-) I try to keep my options open, but there are some things I prefer: -It should be a hell of a lot better than the crapy onboard AC'97 sound I use right now (SNAP-CRACKLE-POP) -It should be external: USB or Firewire or otherwise are all OK (I'll be using it with my desktop now, but I plan on setting up a laptop for music some time) -It should be affordable: I can always make exceptions here (especially since I'm not very familiar with this type of hardware), but I'd prefer if it were around $200 USD or less. -It should be *exceptionally* functional with Linux and JACK. (Naturally, this is best proven through experience) -Although the above should cover this, it ought to work with my Novation X-Station synthesizer (which already works great through USB with JACK) I'd really appreciate any recommendations -- or blacklists (although ALSA's soundcard matrix usually faithful enough) -- of hardware to be used by a novice electronic musician. I try to be brief, so if I'm being too ambiguous just ask me for details! Thanks, -Lou