The adjustable shelves will rest on the usual shelf pins.  All of the shelves will be the same size with indents on the underside to index the shelf pins (to prevent them from shifting).  To ensure that the front edge the shelves will have a uniform offset from the slanted front regardless of where they're placed, the line of shelf pin holes needs to run parallel to the slanted edge of the side panels.   

I made a drilling guide for use with a plunge router with a 7/16" guide bushing.   The 1/4" dowel indexes the slanted front edge of the side panel to establish horizontal offset of line of holes from the front edge.  The drilling guide holes are 1" apart vertically.

I tried the guide on an off-cut to make sure there would be no issues with veneer tear-out when drilling.  All holes had a nice clean edge.

With a partial dry fit, I first did a sanity check with the guide placed on each side to make sure the holes would line up properly. 
After working out where the lowest pin hole should be located, I made a spacer to keep the guide parallel to the fixed shelf surface.

With the panel clamped tightly in place, I drilled the first set of 11 holes front and back.

I needed 16 holes altogether, so after drilling the initial 11, I made some 5" spacers to shift the guide up 5 holes.  I aligned the guide laterally by eye, centering the guide holes over the previously drilled shelf pin holes.  Ideally, I could just rely on the 1/4" indexing dowel to set the lateral position.  However, I made a slight goof when cutting the taper on the side panels.  They were not cut at exactly the same angle, so they diverge by about 1/16" at the top of the panels.  I could use the indexing pin on both sides at the lower end of the taper because they haven't diverged much at that point.

With the guide clamped in place, I drilled the remaining 5 holes front and back.

I'm happy with the results.  The other side went just as smoothly.

I bought some extra long 5mm shelf pins, 1" total length.  I had some soft tubing that had the right inner diameter to slip over the pin.  This will provide a little bit of wiggle room should a given elevation of pins not be on the same plane (or if the shelf is not perfectly flat).

To test for planar pins, I used the bottom panel as a makeshift test shelf. (I won't complete the adjustable shelves until after the cabinet glue-up.)  I installed the panel at a couple locations, and I could only detect the slightest rocking.  With the weight of a component on top, it probably won't be noticeable. 

Next I'll work out how to get cables routed in/out of the cabinet.