Well, I have recently bought a Magnum Dynalab SR100 Antenna for 50 Euros here in Portugal (35 USD on the Magnum Dynalab site) to replace the "wire" that came with my Sony tuner, and got a reception improvement of 4-10db, depending on the FM station (still 10db away from the theoretical tuner maximum reception, though...). So the use of one of this model or its big brother, the ST-2FM (99 USD...), both indoor models, does help reception ... a bit; however, I believe you'll have to go the outdoor or signal amplifier path if you are to get a big improvement.
Hope this will help.