asynchronous USB dac or jitter reducing device

I have a Red Wine Clari-T driving a huge single driver baffle. The range is roughly 80hz to 15k. I am interested in a macbook based digital system using Wifi or usb. The only piece of the puzzle I have is the MacBook. My budget is less than 1K including airport express or other similar, an asynchronous USB dac and or a DAC and pace-car type reclocker for jitter. If I have an asynchronous USB dac do I need a separate device for jitter? The Pace-car is clearly out of my budget, so what are my options?
Thank you in advance.
2nd Benchmark DAC. I use it with MAC-Mini/Airport Express. Stretch your budget by $150 and get AE ($150) and new Benchmark DAC1 ($995) to obtain 5 years warranty and avoid problems that early Benchmarks had (thin sounding op-amps, high output impedance on unbalanced outputs).
Dacmagic for even less.
Try an EMU 0404 - with balanced outputs - $185 does the job, sounds great. Yes, audiophiles will not like the plastic case but it works.
I can appreciate that some of the less expensive DAC's listed above are good buys. However unless you can reduce the jitter you probably won't be happy with the sound quality. Take a look at the Benchmark DAC1 USB. It will reduce the jitter and the USB version has their best OP amps. Should cost $900-$950 used here on Agon.

There may be others as well, but the jitter reduction is worth the investment.