Long USB Cable OK?

I just purchased an Ultra Fi iRoc DAC (haven't received it yet), and intend to use it with a media PC that has iTunes (I've all my CDs on the HD on Apple Lossless format).

Question I have is whether it is ok to use a long USB cable from my PC to the DAC? Currently my PC is about 18 feet from my Audio System. I can then connect the DAC to my Preamp with a very nice analog pair of ICs (1M pair of Acoustic Zen Absolute - I think retail on those was about $2.5k). Also, can I use a regular length USB cable and an extender (I have an extender already, so am just wondering if I can use that too, without any sonic impairment)?

Alternatively, I have a very long length of cheap analog ICs I can use (and keep the DAC close to the PC with a short USB cable).

I keep the PC out of the way because its noisy and prefer not to have it alongside the audio system and speakers.

Any advice welcome. Thanks!
John.