Unfortunately due to the bandwith and limited range of the radio signals as well as the number of FM stations you can receive, you won't be able to get many stations outside your range of your antennae. You might be able to get a higher powered FM Receiver, but you will realistically not be able ot get ALOT of extra stations. Just make the ones you can receive stronger. The issue there is say if youlive in California, and you can receive a station say....99.9 fm. Well you dont like it...but you like the 99.9 in Oregon.....your fm receiver would not be able to tell WHICH 99.9 signal to use....so it probably will sound like crap because you may be receiving both stations at the same time...or you can't localize which station it can pick up.
The BEST solution to this would be to go with Satellite Radio...
XM and Sirius.
Thats all I have for ya..good luck!