In most cases you dont need to change antenna for a 1000 sq ft house using a typical router if you choose the placing prooerly. The reception is also down to your clients as well as how many walls and entry point for your router. Therefore real life results could differ.
From my experience I had a setup with the following
1. WRT610Nv2 covering around 1300 sq ft with full coverage around
2. DrayTek 2920n with 5dbi antenna covering around 80% of 2500sq ft
3. DrayTek 2130n with 3 dbi antenna covering 2 floors of around 95% of 700sq ft per floor
.
Anyway please provide more information about your plan and budget.
Generally you can consider DrayTek products as most of them will allow you to change antenna whilst a lot of the other systems. You can choose from a setup with one router as well as a router with an extra AP if you wanted to.