Macbook to USB to which one?

Bwp,
Thank you! That is exactly what I needed to know.

Doesn't the Macbook have the headphone out which is also a digital output? You can buy a simple plug that converts the headphone out to toslink. Then you don't limit yourself to USB DACs, which really takes the better DACs out of contention. I would double check your manual to see if the headphone out also doubles as a digital out. I have three mac laptops in my house (mine, son and daughter) and all of them have the digital headphone outs. Two of them are already 18 months old.

After a lot of research, I hooked up my MacBook Pro to a Wavelength Proton DAC and never looked back - sound is excellent. Main reason for selecting was the performance with a USB connection.

I bought a Centrance DACport a few weeks ago to use as a portable USB DAC + headphone amp for my MacBook. The thing is TINY, but the DAC is really really good. I also now use it in the office to play my computer tracks through my speakers (Rotel separates + Meadowlark Kestrel Hot Rods) and am amazed at how good it sounds - esp. with high-res tracks or high bit-rate internet radio like the Linn stations.

Centrance also just began selling the DACmini, which doubles as a headphone amp (and pre-amp, I think), but it's more money (http://centrance.com/products/dacmini/)

According to Stereophile, Centrance licenses its jitter-reducing technology to Benchmark, Lavry, Bel Canto, Empirical Audio, and PS Audio, among others. Well worth a try.

I'm getting outstanding results using iTunes > MacBook > USB output > Ayre QB 9 > balanced out to my integrated amp. Very basic, with excellent results. The only sound I hear is from my speakers.