DSD-PCM question

I'm a little confused about digital transmission issues as they relate to frequency response, and hope someone may have a clear answer for me.
I would like to stay in DSD all the way downstream to just before my power amps. If the signal is converted to ASE/EBU somewhere downstream, doesn't that effectively cut out all response above 20 khz? What is the point in high-rez formats if the signal is compromised downstream? I plan to be running supertweeters, and want to use the SACD to its capabilities.
My system currently is:

Sony SCD-1 w/ VSEI level5 (upgraded signal only on analog XLR)
Supratek Sauvignon linestage
DEQX 2.6 w/ digital in/out option
Butler 5150 to 10" Peerless subs
Tenor 75wp monoblocks to mids
McIntosh MC275 to tweeters
Linkwitz Orion 3-way wired direct
Revelation audio labs balanced IC's

Any suggestions /recommendations are appreciated. The reason for this post is I'm considering replacing the Sony and Supratek with an all-digital source and pre to do away with one DSD-PCM process. Would it be worth it? - any specific recommendations?
I may be wrong, but I'm pretty sure that currently there is no standard for outputting a DSD datastream. SACD players with a digital out just put out PCM. There are some proprietary DSD transmission interfaces, i.e. EMM labs, Accuphase, and Dcs, but those are closed systems, meaning the DSD signal goes to the DAC where it's converted to analog and then outputted. If anyone can either expand on this or correct it please do. FWIW, you have a very nice analog system already, are you sure you would be improving things by going the route you're considering?
I believe Jond's understanding is correct. Your best bet to get the full bandwidth DSD offers is to use the Sony's analog outs and put no further digital equipment between the Sony's output and the amplifiers. If the DEQX converts the analog signal to pcm, you've lost your bandwidth; I don't know of any digital crossover that uses DSD, though I'm willing to stand corrected, because I don't know very many.

I'll leave it to cable experts to tell you whether a balanced interconnect would restrict the bandwidth--I would think not. The only limitation on a cable should be the signal it's fed.