Lawman,
I just want to make two comments here. First, I probably should have commented as you did about the kind of truck required to tow a 20,000 lb. GVW trailer. With everything around from an S-10 to a Peterbilt to use I sometimes forget to consider such things. You make an excellent point.
Second, I'd like to respectfully disagree with the following;
<font color="blue"> we need to work this equation in reverse, vehicle, what your towing and then the right trailer setup</font>
As a truck dealer, I have people coming in all the time looking for a truck because they're going to need something to tow a trailer (horse, equipment, RV, whatever) they intend to buy. As much as it seems to be against my best interests, I tell them to go and buy their trailer first and THEN shop for a truck. I don't know what truck will fit their needs until their needs are established and that doesn't happen until the trailer is picked out.
As to the order for a general use trailer or equipment trailer, I think the order should start with the load/equipment you intend to haul. I think with most people that's what starts this whole process. They either have or want or intend to get something they're going to need to trailer. That's the first decision they either make or have made for them. In either case, that will determine what they need in a trailer both in terms of physical size and weight carrying capacity. Only when those two are in place are you ready to get the truck with which to pull it.
If you start with the load, each subsequent decision in terms of capacity is pretty much a matter of doing the math. If you start with the truck it's like that old football adage about passing--three things can happen and two of them are bad. /forums/images/graemlins/grin.gif You could get just what you need, of course. More likely, however is that you either end up with a truck that's not able to do the job or is dramatic overkill. With a truck not able to do what you really need you can end up limiting your choices on the other end based on the truck you bought. With the oversized, overpowered truck you end up spending way more on the truck and fuel for it than you need to. I just never want to be the guy who sold that truck in either case so I tell customers to get the other part done first. It makes my job easier and keeps them happier in the long run. /forums/images/graemlins/smile.gif