I recently bought wire shelving from The Container Store (you can probably find another store, too). The consumer brand is InterMetro and the commercial is Metro if your equipment is very heavy. With InterMetro you can choose black, white, or silver. It is modular and adjustable. I had the poles cut to 50". The wire shelves are all 24" wide, perfect for home theater gear.
Let me tell you, having the rack on wheels is amazing! Setting up and making changes is so easy. If you go wheels, the 3" casters are limited to 100 pounds each (so a 4-wheel, 4-pole rack can hold 400 pounds). I got 2 plain wheels and 2 with brakes.
I chose black which looks pretty good with black gear. I have 5 shelves total at varying positions (each amp and preamp have their own shelves). My bottom shelf is at the very bottom of the poles, holding a 75 pound amplifier. The top shelf is at the very top of the poles because it would look silly to have bits of the poles sticking out. All the feet on my gear contacted at least two wires of the shelf for weight distribution. You could add coasters to spread out the weight if you'd like.