I ran a B&W broadband folded dipole for a while and found that it had a much lower noise level than a regular dipole. Unfortunately, it didn't transmit well below 7MHz (above 7MHz it worked great).
You could build a home brew version for receive only for a fraction of the cost. See http://www.cebik.com/wbfd.html
Or, if you have the room, build a loop 70 ft on a side. That will allow transmission as well as reception and will have a much lower noise level than the vertical.