"The best way I can describe the sound I’m wanting to achieve is smooth reference..I favor a bit of brightness and separation is important to me...none of that information may be important when choosing a digital component but I thought I’d share."
Brightness in a digital system is not always the same as in an analog system. There's several reasons for this, so just keep it in mind as you do your research. Separation, dynamic contrast and imaging are definitely qualities to consider when selecting digital gear. Analog tends to replicate these things with very little trouble. Digital can do them as well, but you have to work a little harder. It doesn't come as easily. Where most people tend to go wrong, is not giving as much attention to the analog portion of a dac as they do the digital side. Both are equally important.
". So Network Player? DAC Attached to my Laptop/Server? Buy a mac mini and attach to DAC? Tubes (since this is a vintage system)?"
With a budget of $700, I would get a dac and use it with the laptop you currently own.