Need a DAC recommendation

If you will only be doing computer audio, then I urge you to research USB DACs. There has been a lot of development recently, and USB now handles high resolution files. There are two approaches, asynchronous (e.g.,Ayre, Wavelength, HRT, Wyred 4 sound) and high resolution synchronous (CEntrance, Benchmark). Within your budget, I recommend you'd look at HRT Music Streamer II+ (the II+ will have much better analog output stage and components than the II) or the II Pro if you have XLR inputs on your preamp. The CEentrance products should also warrant your consideration.
Is the high resolution USB as good as the digital coax? Depends on a lot of variables. How are you getting coax out of your computer? Musical Fidelity V-link or M2Tech hiFace Asynchronous USB To S/PDIF Converters? Or just a basic computer soundcard?
I am assuming the latter. Why don't you borrow the Musical Fidelity combo from your other system, and hook the V-DAC up both via coax and through the V-Link, and listen which connection sounds better. That should give you an idea what direction you should go, coax or USB

Audio GD nfb2 is fantastic value

The VDAC is a pretty spectacular unit considering the cost. Not sure your budget is going to jump you to another realm of performance unless you look to some of the older hi-end units mentioned earlier. Another one to consider from the same company is the MF Nuvista DAC of which I have never heard an ill word spoken of it.

Arni--you make a good point about borrowing the combo from my other system. For some reason, I haven't thought to do that(I have the V-DAC/V-Link set up at my gf's place) but I will bring it home and compare the v-link with straight coax into the v-dac. BTW, my soundcard has a dig coax output, and that's how i'm getting it.

In regards to the argument about having a good power supply, I agree, but this raises the question: how does that reflect in the quality of the HRT DACs, which are only USB-powered? In addition, would you say its worth adding an external power supply to the V-DAC? At that point it might just make sense to go for the M1 DAC. I haven't heard any mention of the Cambridge Audio DacMagic--how's that compare? I'm also curious about the Emotiva XDA-1 DAC, which I hear a lot of people talk about. Has anyone had the opportunity to directly compare anyone of these great value DACs(emotiva,MF,HRT,PS)?

P.S. If anyone cares, these are my current setups:
1)Totem Rainmakers + NAD C375BEE (Love this combo)
2)B&W CM7 + Rotel RSX-1056 + V-Link/V-DAC (Like everything except the Rotel)

I think you have a great combo with the rainmakers and the C375BEE to start with!
A lot is going to depend on the quality of the digital out of your soundcard- i.e., what route to take. The V-DAC appears to be one of those rare over achievers at its pricepoint- except for USB input. I don't think the Cambridge DacMacic or the Emotiva will make any more real music.
The PS Audio Digital Link-III recommended above has a discrete output stage (no opamps), 192k capability, and on the used marked, is a great value. I'm positive it will better the V-dac. However, its USB input is old school limited to 48/44.1. It would be my recommendation based on your original post/question (coax digital in), but I suspect that the V-link will outperform your coax soundcard-output by a huge margin.
You raise a good point about the power supply to the HRT streamers... I don't know how they do it... but they claim to isolate the power from the audio - and it sure sounds good. Don't overlook the CEentrance Dacport XE, it may even be better than the HRT.
In my main system I have Cullen modified (stage IV) PS Audio D-Link-III fed by Squeezebox Duet. The sound is extremely airy, neutral detailed, but still warm with strong bass. I have never heard an un-modified unit, but I suspect similar virtues would be there too. You could pick one up used for about $450-$500, and add a good USB to Coax converter that does 24/94- or even 192- and be just a tad over your posted price tag.... or do a HRT Streamer II+ and be done with it....