You always need to come up with an appliance selection during the design process because they can influence the design of the kitchen.
Consider re-sale value when picking out your cabinets. What you buy today may or may not help you with the re-sale value of your house if you plan on selling it in the next 5 or 10 years. You may want to consider cabinets that are marketable to help with the sale of your home.
Never sign a contract with anybody until you have seen a visual presentation of what it is going to look like. Get everything in writing and verify the contract, license make sure it is a reputable company and get references. Make sure they are insured.