New Intel Mac-mini to external DAC

I currently have a two-channel system, that while high-end, sits firmly in the budget category (b&w cm6s, rotel 1070 pre-amp, 1080 amp and an arcam cd73). I also have a squeeze box that allows me to access my digital music from my mac laptop, and it sounds great. The problem I have is that the squeeze box doesn't sound as nice as the Arcam, and the laptop hard drive is nearly full (all my files are lossless). The difference in sound quality is most likely coming from the DACs in the two devices, as I'm using the same interconnects on the Squeezebox as the Arcam (kimber heros) and there is still a difference in sound quality. I would like to match or outperform my arcam with a computer/hard-drive. It seems that i should be able to purchase the new mac-mini for six hundred bucks (and also by an external harddrive), rip the rest of my cds, and then send the data to an external DAC and get better sound quality than my arcam. What I'm trying to figure out is what kind of DAC I should be looking at? The wavlength brick usb dac looks interesting, but seems a little pricey at $1750. And I'm not sure what the advantages of the USB connection really are (is jitter really a problem?) Can I run optical out of the new intel mac mini to a less expensive second-hand DAC? What are the advantages to going USB? What other options are available that will match or exceed the sound quality of the ARCAM? I would appreciate any thoughts.

Thanks.