How can a PS Audio Perfect Wave DAC enhance my system?

Make the call to PS Audio.  As Iwin stated the PSA DAC will play your digital formats.  The raw DSD layer of copyright protected SACD goes directly into your PS Audio DAC through I2S only.  

Rich 

My Popcorn Hour A-500 has an ESS SABRE ES9023P audio DAC and plays all my digital formats including my library of DSF files.  Same with my Marantz SA-14S1 SACD.  It has a Cirrus Logic DAC and performs as you would expect from Marantz so I am not sure why I would want to bypass the Marantz DAC on the notion that it might sound better.

I'm sure if I called PS Audio they would take great pleasure in telling me why I should use their DAC.

I had an opportunity to pick up a PS Audio Perfect Wave DAC.  I read the DAC connects directly to the power amp, in my case a McIntosh MC500, so what do I do with my McIntosh C48 preamp?

It connects either way unlike your claim of getting DSD out of that Marantz. Notion? Sounds like you're in the wrong hobby.

I ran my my PSA DAC with a Sony UBP-X1000ES with a Chinese HDMI to HDMI I2S adapter so it would decode the SACD Layer of any disc or DSD file.

Fuzztone, thank you for your stellar contribution to this thread.