My wife and I just went through the same process. We had 4 people come over and give suggestions. I asked each to give me a detailed itemized quote, broken down by section (ie. such as pool, lighting, landscape, fence) and then each item under that section ie. pump type, filters, type of lights, type of pool, concrete, etc.).
This way we could be sure of everything we would/could get (a checklist), understand why we needed it and what to expect from each contractor when the job is complete. A checklist is extremely important! We had 2 of the contractors not supply the information, which let me know they most likely had something to hide and I wouldnt want them in the end anyhow.
Ironically, after finding that our expenses went from an expected 25k to around 40k, with taxes and finance charges, we decided the kids and the two of us can wait a few years.
Ask questions, get answers, document everything and understand the process. Its your money and you should invest it wisely to get exactly what you expect.
Be sure to check their quality of work by visiting a site or two as well. And keep in mind their quote generally does not include landscape, exterior lighting if desired, fencing and some concrete.