Wood I feel is the right material, especially if solid and not too much MDF is employed. Don't recommend glass, stone, ceramic, steel, aluminum, etc if you ask me...they may tend to have too reflective of an RFI/EMI profile in your room and/or vibrational properties with your components. Although thick acrylic used as shelving can be an exception to that, I believe. Just make sure your wood joints and seams have as high a contact surface area as possible to minimize long-term cracking due to expansion/contraction. This may really be the worst bad rap concerning the run-of-the-mill wood racks. Bracing can help there, if needed. Use glue on all joints regardless of whether or not you use fasteners and ONLY use the regular, old, yellow wood glue...as with speaker building, using any other glue type can audibly increase mechanical vibrations - even if the adhesion is solid.
Also, give consideration to lowering the height, not just for the good reason that Albert points out, but also to take the opportunity to lower the rack profile if it's going to stand between the speakers and that will let your speakers image that much better. If the rack is to have doors in front that remain closed during use, consider a backless cabinet design for ventilation, if aesthetics are not that high of a priority whenever the doors are opened, as the wiring may be visible then. But, the wiring going in and out of the rack may be easier to route that way.
You can even use a particular kind of learning remote that can transmit in radio frequencies, along with infrared, so that the signal will pass through a closed wood door to a special, small radio receiver which outlets to tiny, wired, adhesive infrared emitters that are placed directly over a component's infrared eye. That allows for remote control of the system with the doors closed, if that's the way you want to roll. Universal Remote Control is the brand I use for that purpose, but there may be others that do the same thing.
Best of luck!
John
