seems like the solution with lightsnake is only connecting an amp in parallel, this means you can't listen only with the computer.
The StealthPlug seem to have "ultra low latency", and I think its possible to play and monitor yourself with computer alone.. What I didn't really understand is if it's headphone output is monitoring only the input or the software's output (although they say it can be used as a live processing rig..).
Looks like the Lightsnake is cooler - but the StealthPlug is more convenient. Still, not sure because I haven't tried any of them myself.
I think that if you're into recording, you should also consider investing a little more in the Lexicon Alpha USB interface, because it also has a mic input, which means you can also record your amp with a dynamic mic.. Or maybe some vocals.. or percussion..
The Line 6 can be also interesting for this purpose, and it comes with amp modelling software and stuff.
Or you can really save your money and go with the M-Audio Jam lab
I think you have better options than the stealth, depends on the purpose (if more towards recording, better to spend a little more on a descent entry-level interface - if more twards practice, the Jam lab wil be enough to do the job at half the money).
Sorry if the links mess up the thread's view width, but I don't know why it is...