In a word, no. You probably have an acceptable budget range. A good design firm will have one too. In order to save both parties wasted time and effort, it's wise to make sure you're in the same ballpark before proceeding too far. The lowest bid isn't necessarily the best choice.
Expertise is big factor.
But, a good design firm will work with you and your budget. That all depends on the scope of the project. Whatever you do, don't send out a blind RFP in an attempt to get a cheap bid. Approach your search with a partnership concept in mind. Think of the selection process as trying to find a strategic business partner.