Best soundcard if have outboard DAC

I am using a toslink connection due to the distance to the DAC. About 20ft. The PC outputs to the overhead projector and hence the distance involved. There is no signal loss or interference with this setup. Sounds great to me. I am using the PC as a HTPC front end / data Base. Here are the components.

KT 800 AMD PC - WinXP Pro
Electrohome 8500 CRT Projector Via PC output
Music Fidelity Tri Vista 21 DAC
Bryston BP 25 Pre Amp
Infinity Crossover
4 Bryston 7BST monobock amps
Infinity RS1B speakers.

If you must use an internal card (not the best solution), then I believe the Lynx is the best around.

When feeding to an external DAC, the sound card only needs to be bit perfect. The DAC does not care about brand names if the output is SPDIF 44.1khz. Redbook standard!!

So, Let me see...

I think I am wanting to go digital out from my PC because I have read and been told that the DAC onboard my Kenwood receiver would be better then any soundcard DAC because of the noise inside the PC etc. First question: Would the DAC onboard a highend receiver indeed be better then the DAC on an external chip? It is a Burr Brown DAC.

Second question: If I am going to rely upon the DAC onboard my receiver, I am relying on a digital SPDIF connection; either optical or coaxial... which is better?

Third question: Is there a difference in quality between different digital outs? Is the sound quality from all 24bit digital outs the same or is there differences? Is the difference in the software or hardware manipulation of the sound before it goes digitally out?

These questions are helping me determine if I need X-Fi, or a lesser card that has SPDIF out? I want to know what the differences are if I am not relying on the analog outs (receiver instead of PC speaker).

I would recommend skipping the soundcard--get a USB audio output device like the Waveterminal U24 that will output spdif. Other cheaper alternatives include the Edirol UA-1D or the M-Audio Sonica. If you use USB instead of coax or optical, it sounds better for longer runs. You will still need a short coax or optical to connect to your receiver (the general consensus seems to be that coax is better, but there are some situations where people claim the optical is superior--you would have to try it).