What do you plan on doing in the barn?
The deal here is 2000ft!!
OK, now if your looking to just say you have Wifi there and not be able to use it. All you need is a well placed Cisco router. That should be enough to see it.
If you wanna use the network... Everything digiblur told you is really the only way. I use a long distance network between my dads house and mine (1000ft LOS). Been through it all on this little hobby. I will never trade my wrt54gs', but they or anything like it, will never cut it. Don't waste a dime until your ready to do it right, it will cost you more and piss you off. You can't use a repeater but for little stuff unless you fork out the money for a high power dual band repeater. Loco M5, simple all in one, 5Ghz, POE. Hell of a price. I have $600 into mine. @2000ft do it right.
You really wanna have fun http://www.ubnt.com/airfiber Holy crap! I think i need to change my underwear now. Is it wrong I just wanna touch it?
Dear Santa...