best load boards

I am leased to a company and have been thinking of getting my own authority and buying a trl. I currently run power/only and basically work for one broker who keeps me pretty busy with one customer. As of now the rate is $2.15 with a trl(lded or mt) and $1.60 BT, with about 40% of mi BT. He keeps me fairly busy but I would need a trl when he is slow. I am not sure if a van or flat/step would be better. I thought I might get a membership to a couple load boards to see what would be best in my area(NE OK, Joplin,MO). I need to stay within 300 mi of the house so I can still service this customer as they usually call and need me to go asap. I looked through my lease and can't find anything about a non compete clause, though my company wouldn't even have the loads if it weren't for me. He calls me and tells me what he has and I call my company and tell them what I am doing. They basically just pay me. I have been driving since 95,O/O since 02 so I know it's a gamble, but anything worth while is. THX