Awesome, you see some of the problems 2 systems will create!

Now, you initially said you have a design for the addition. Then later you said "Many have no desire to do any detail planning until money is flowing..."

What is your design comprised of? Are you working with an architect, or is it rough sketches of your concept?

Bid Spec means you have completed designs you take to bid. You'll need an architect or engineer.

Design Build means hiring a contractor and working with them on everything. That means choosing the guy you are most confident can effectively help you realize your vision and starting the money flowing.

Either way the money needs to start flowing to get good design on paper.