Looks like you have received some excellent advice! Just wanted to add my 2 cents worth - I have an older (2001) Giant Innova hybrid - aluminim frame. I am currently training with full panniers and front bag and it is doing great. Maybe not the fastest ride out there, but definately can handle the added weight, plus I have had to run out onto hard pack trail and grass a few times due to road hazards and it handles the terrain beautifully. If you decide to go the hybrid route, you can always change out the tires to slicks and gain speed. I have not topped out the speed on my hybrid, but yesterday I managed 14 mph with fully loaded panniers. Good luck with your search and post when you find your new ride!
“No Bird Soars Too High If He Soars With His Own Wings” ~ William Blake