Best DAC for $500

Just starting assembling my HIFI system.

Speakers - Snell Type D's - Biwired
Amp - Sunfire 2 Channel
Pre Amp - Parasound

Almost all of my music, 20,000 plus songs, is on my PC. Listen to my music either via I Tunes or Windows Media Player.PC does NOT have an upgraded sound card.

Very diverse music listening, from Rap, to classical, to metal.

Trying to determine if my best move is an external DAC,and if so the best for my current set up. Or an upgrade at sound card.

Help appreciated
I have seen used tranquility USB dacs go for $500, and eastern electric minimax dacs go under $600. Probably the best one can do in that range.
I'm looking into the DACMagic Plus. The ability to directly drive an amp, the headphone output AND the BlueTooth Dongle are all selling points to me. Not to mention the async USB and a pair of tos/coax inputs. Very Flexible.

All-up with the dongle? More than the 500$ limit, but with 4 digital inputs, I couldn't imagine needing more.

Better out there? Should be, but at what cost?
...and as usual, no one has even mentioned the Emotiva for 249...

Yes, I bought it.
AFTER already asking myself this exact question, then answering it.

You would need a $27 Behringer to up the USB output to 24 if you want to go direct to the DAC...but I would suggest buying a squeezebox touch.
You would still be under 500 for both units and you would not have to have your PC tethered to your soundsystem.
There have been several DACS that sounded great. Honestly, there is very little that keeps a 100 dollar unit from being a 500 dollar unit.
Ask about the Emotiva on special from their site right now. I love mine and it sounds very very good. No nasty sins at all and a lot better than any 2k CD player I have heard. (I have heard about 12 of them recently)
A used Ps audio DLIII. Makes many dacs in this price range look like toys. Just look at the power supply and output stage and then listen to see if you like the sound of an upsampling dac. You can also choose between 96 or 192 upsampling which is a nice feature depending on the rest of your system.