Check out the shelf construction I use at www.k8ac.net
. The black vertical tubes are from Sanus TV/audio component stands and are very substantial steel and are secured to the shelves with 1/4" threaded rods. The shelves are 3/4" oak veneer plywood with iron-on oak tape edges. The posts come in several sizes and can often be found on eBay. As you can see, the structure handles my beefy Alpha amplifier quite well and it gets a high wife approval rating. And - it's fairly easy to modify the shelves to accommodate changes in rigs.