If you have a cheap Sony, then you could get a better one. I despise the Sony multi (200, 400 disc, even the ES models) players as they sound absolutely horrible even through a DAC. The really cheap ($200, $300 when new five disc Sony) also suck. Look for a Yamaha, or a better Sony, the ES series five disc only..
The Adcom DAC is good. I tried a Bryston and it was no better than my Adcom DA700 which can be had used for $200.
If you want to build for the future... start thinking about a server from your computer. it is a messy knowledge driven form, but worth the effort, and it IS the future of digital audio.(i still am stuck in my changers.. but the future is clear.)