Things to Consider:
1. What is your budget?
2. Do you like the sound from your current setup?
That being said, most articles I have read, many from this site, and through my dealer, the most important speakers to match are the Fronts and Center, this is where a majority of your sound will originate from.
You probably will have a difficult time to match the rears, or surrounds, but at least it won't have as much impact on your sound.
There are tons of options for in wall and on wall, but before throwing out any suggestions, you would need to determine your budget.