There are also, some great tools that will auto populate many sites at once like Trulia, Zillow, Hot Pads and more. For example, postlets.
Ask you realtor to look into a program that auto populates all the major sites at once. Some of these are free!... more
It's hard to say with any real authority but having built many homes over the years as well as done many extensive renovations similar in scope to what you've described I'm leaning toward building new as more practical and economical when the finished product is considered.
One thing you need to think about is whether if you stayed and renovated/rebuilt your home if you might not end up as an over improvement for the neighborhood . If you feel like you may end up as one of the more expensive homes in the neighborhood this would definitely indicate you should not proceed with this plan.... more