Well one solution that would work out ok if your not planning on moving the cabinet around also, is to route out a small groove along the monitor shelf creating a groove that the glass can basically sit in, and rest up against the speaker shelf, or againse the front of the monitor. Its not the prettiest, but it'll work. The other stolution that also doesnt look the best but you can sorta make it look ok, is if you use 2 Aluminum (you can get it in black) L brackets from home depot, which is normally used for siding i think. anywhoo, attach 2 of them 26" wide one on the top (under your speaker shelf) and the other on the monitor sheft, and have the glass sit in the groove of both of those. if you attach the top one first, then insert the glass, then attach the bottom one to the glass and slide it in so that it sandwhichs itself between the glass and the monitor shelf, then it'll stay pretty snug, you can also use a bit of glue or something to keep it secure. Then you'll send up with 2 bars, across the top and bottom (you could also do it for the sides) and it give it a nice little frame that you wont really notice after a while. (especially if they are the same colour as the cabinet or bezel.