I owned the GCD-575 for about 6 years. When the unit was first released, it was quite good, offering very good build quality and good audio quality. I was very content with my 575, and replaced it primarily because the laser burned out and the repair cost (more than $200) wasn't cost effective.
The 575, by today's standards, uses fairly outdated componentry, and I don't think it's worth the $150 price you mention. If you are willing to spend another $100 or so, you can get a newer used unit that offers improved performance, particularly if you are going to use an outboard DAC. You might want to scan the A-gon archives, or post a new thread, to get info about which decks would be good as a transport unit.
The 575, by today's standards, uses fairly outdated componentry, and I don't think it's worth the $150 price you mention. If you are willing to spend another $100 or so, you can get a newer used unit that offers improved performance, particularly if you are going to use an outboard DAC. You might want to scan the A-gon archives, or post a new thread, to get info about which decks would be good as a transport unit.