You have already gotten some great answers on the schools and some of the developments, so adding to that would be a disservice to those who already shared their expertise. I wanted to talk to you about custom & semi-custom. Semi-custom is where you like a floor plan that a builder has, but you need to tweak it a little, add a bath, push a wall out, or add a room. Amberly was mentioned, and there are some semi-customs out there, but the lots are really tight, and therefore a little limiting on what you can do. The price range that you are comfortable with, may leave you not as many options as you would like if you want to stay in West Cary. There are some other options if you go to the southern end of Cary, tucked in next to Apex & Holly Springs. I would like to talk to you about your commute time, and your overall goals before recommending that area.
Your other question, about a buyers agent on custom homes. A buyers agent in general is in my opinion, a must have for a buyer. Buying a home is a very emotional time, and a good buyer agent will interject logic into the process and keep things smooth. A buyer agent will be representing your best interests, the agents for the builder represent the builder, not you. It would almost be like going to court and trying to representing yourself, not recommended. There is actually more work involved in a custom home, and a buyers agent will prove even more invaluable if you are relocating, and not in the area, we can help out a lot with some of the legwork. I myself, built homes in my teens, and have done many renovations throughout my years as a homeowner. I am very particular when it comes to how homes are built, and I have a very good eye. That would also be very beneficial to you. If I can be of help, please contact me through my profile or website. I would be honored to help you create a wonderful new home for you.