CAL Audio CL-15 or CL-2500 for redbook playback??

I would recommend the CAL-2500. Read the Stereophile review and the Widescreen review. It uses a heavy duty transport and the electronics are heavily regulated and isolated. I bought it to just to drive my Reimyo DAP-777, because it has a balanced digital output. There is someone who bought up a lot of the stock and is selling them for $830 a piece. That's what I bought, brand new in the box.

I'd say the Cl-2500. It's the last design the company produced. If you have a dac capable of handling it, the Cl-2500 upsamples.

I remember the CL-15, a friend owned one years ago.
Great sound, I almost bought one myself.