Maybe I'm missing something, but if you don't own a single CD, how are you ripping your music? If you don't rip your music in a lossless format you will not get near the resolution your mac mini can achieve. Also, jitter is a big deal but if you don't have a good dac and your music isn't in lossless you will never get close to vinyl. The Havana dac used is about 6 or 7 hundred dollars and will get you a lot closer to your records. Another good dac if you can find one used is the metrum octave.
Good Luck,
Greg
Good Luck,
Greg