Blu Ray player versus CD/SACD player.

+1 From @mahler123 

this is the best advice you will ever get, full,stop.

@mahler123 Wonder if you could explain the 2nd part of your response further? “and for redbook I use one of the S/PDIF outputs into a mini DSP (room processor-it won’t work with SACD).  Before I had the mini DSP I just used the HDMI output for everything.”

Not familiar with mini DSP set-up that you mention?

However, adding an upgraded external DAC and using the Oppo as a transport is a fresh idea I might consider?

Budget would be $3-$5K, for either an external DAC or CD/SACD player.

The most important part of your question was “will I hear a difference…”. The fact is, you can buy a $7500 Marantz or $16k Luxman and you may not hear a difference. Nobody can predict what you will hear. My advice is to find a dealer and ask if they can set up a demo for you, comparing your Oppo to something more expensive.  If there are no dealers, many online outlets offer 30-day trials, but know that there could be restocking fees.  If you own a lot of SACDs, you will need a stand alone player like the Marantz SA10. If not, you can add a dac to your Oppo for improved cd quality, but it won’t play SACDs. A lot of balls in the air for right now. Btw- the Oppo is not a bad player at all. I don’t think digital technology has really improved over the last few years. It’s really more that very good dacs are now available at much lower prices. 

A number of SCAD/CD player options aside from the Marantz SA10

What preamp are you using? and how is the Oppo connected to it?