Sigmatel Audio Workable?

It depends what you mean by workable.

Sigmatel, Realtek, SoundMax and Crystal Sound have no interest in producing on-board chips for music production so no low latency drivers, clocks are locked at 48kHz, etc. but with Asio4all and a realistic view of what you can achieve you can use them.

BTW this isn't the right forum to get advice on this and I expect the mods will move it to the Hardware forum and you haven't said what you want to do with the Sigmatel and Cakewalk software but there is no reason that you cannot use the Sigmatel and, say, a laptop to do a mixdown of already recorded material whilst travelling. Possibly add a few tracks with soft synths provided that you don't want to use too many effects processors (especially the high load ones like the linear phase effects).

Perversely, you actually need more experience/knowledge to use the simple audio interfaces. The more expensive units from companies in the music production business are easier to use.

Phil