your best is to use a site survey software (ie Ekahau is one) to figure out which model you will need. It is more than just providing coverage, it is also about capacity and not just in terms of # of users.
1. What applications will they be using? 2. What types of devices will be used on the network? 3. Are all the users concurrent? 4. Are there any VOIP requirements 5. Ceiling height 6. Type of materials inside the warehouse. 7. Where do you want coverage? 8. # of devices per person