The best remote on the market, in my opinion, is the Home Theatre Master MX-500. One of its many impressive features is the strength of its signal. My gear sits behind a couch and the MX-500 works it without fault. But definitely try before you buy. Bob is right about the fact you may have to use a repeater, but it tends to clutter the room, spray copious amounts of RF around the place (even when you are not using the remote), and can be incompatible with some equipment (One I have will not work with either my Placette preamp or an AMC preamp in my daughter's system).
Go to remotecentral.com to check out what remote is best for your situation.
Go to remotecentral.com to check out what remote is best for your situation.