Triple wide racks are going to more expensive unless you go modular. Double wide 3 shelves high will be less. Most of the racks made are not made to hold 100lbs. plus McAmps.
Low end price wise VTI or Lovan.
Billy Bags, Sound Anchors or Timbernation will build to specs.
Lovan Sovereign AV Rack 3 tier 43" wide 3 tier av rack
VTI BL503 - BL Series 3-Shelf TV Stand
www.billybags.com
www.timbernation.com
www.soundanchors.com