I want to buy an audio interface to record to my laptop with high quality through the vypyr 75. The vypyr has it's own "studio-quality" USB record out. Will buying an interface make no difference at all? Because if I record right now with just the USB cable straight into my laptop's sound card, the sound is very crappy with extra uneccesarry buzz.

However the description in the manual says:
"The VYPYR USB requires no drivers. Don't worry the output is microphone/cabinet simulated and will sound great right into your computer."

This makes it sound like that the vypyr will sound just as well without an interface. Is this true, or will an audio interface greatly improve the recording quality? I'm hoping to use the headphones line out directly into the interface, because i don't think there are any audio interfaces which take USB as input.

tl;dr - So is it unnecessary to buy an audio interface while using the vypyr? Or will buying an audio interface improve the quality of my recording?
Should be fine without one. An audio interface is mostly for preamplification of the signal, which your Vyper already does.
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any home recording isn't going to sound that great (unless you buy studio quality gear). The idea of home recording is to either not forget what you wrote, or make something passable for myspace; such that a record company will find you and put you in a studio...
the USB does NOT plug into your soundcard...the soundcard is the headphones, speakers, and line-in on a computer...

so no, an interface wont make it sound MUCH better... key word... you could mic your amp, but then you're spending like 300 dollars you really didn't need to for a barely audible difference
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