Wouldn't an external usb sound card take full advantage of the Swan M200 Mkiii speakers or would a Macbook Air be sufficient?
Update:
Or would a Macbook Air be good enough, therefore, a usb dac would be a waste of money?
a lot of cheap usb sound cards will color the sound to the point of distortion, which will be noticeable with any decent speakers. Still, straight out of the audio jack wouldn't be too bad either otherwise go with a decent DAC. See head-fi for ways to empty your wallet lol. I use a headamp pico (dac/amp) from my head-fi days to drive my Audioengine 5s.
The MBA doesn't have an optical out so you will need a USB DAC. Get something like a Fiio E10. Its like $60. Whether it is worth it for your Swans I don't know (probably yes at that price since external DACs are usually better due to electronic noise etc) but it also gives you more options in terms of headphones as it functions as a headphone amp as well.
Would the Filo E17 work?
waloshin -- if you have any kind of audio recording in mind -- such as voice via XLR mike -- then another possibility would be something from M-Audio or Digidesign.
I've used the M-Audio Fast Track and the Digi M-Box2 Mini for making recordings, and when I'm not doing that they both also function well as USB DAC boxes for feeding my powered speakers. Of course that's not their primary function.
With the Fast Track USB at about $120, you also get a copy of Pro Tools SE. If there's no recording in your future then it's a hardware and software waste.
Any DAC under $500 is a waste of money. All of the cheaper ones use the exact same chipset as in your MacBook to begin with. The only difference will be a slightly better output stage. The problem with any USB DAC is that USB loses fidelity due to power leakage to and from the motherboard.
You're best off to get a good amplifier and 1/8" to RCA cable (check out Oyaide interconnects). That combination will get you better sound than a cheap DAC.
If you want a good DAC, the Cambridge DacMagic Plus on the budget end of things, the Audiolab M-DAC in the mid-range, or if you want crazy good sound and have cash to burn, get the Weiss DAC2 or DAC202.
Would the Tascam US 1800 be of any higher quality?
Would the amplifier in the Swan M200MKIII be good enough?
As for robdpittman's comment, anybody who's suggesting interconnects from this family
http://www.amazon.com/Oyaide-NEO-RC...ie=UTF8&qid=1339413219&sr=1-1&keywords=oyaide
is living in a different world than the rest of us are. I know these are RCA/RCA but I suppose that RCA-1/8" interconnect is priced similarly.
The NEOs are approaching the top end of the spectrum for their RCA interconnects. The RCA-mini goes for $90-$120 depending on the length, and you'd be amazed the difference you can get out of a good cable.