JimB - amps only work with the signal coming down the wire. A good tuner may have a far better RF amp than the relatively inexpensive amp in a tabletop amplified antenna unit and that small tabletop unit will only intercept a small amount of the RF wave from the transmitter.
Frequencies vary, and so does the optimum size of the dipole antenna element that is best to pick up those varying frequencies. Lower freq - = bigger/longer dipole to best resonate with it and grab the most signal. In a former life several decades ago I had a 10-element, double-driven yagi antenna on a tall rotating mast to feed signals to my Sony ST-5130 tuner. Located in Fort Wayne, Indiana, by careful aiming I could pull in either Chicago or Detroit stations. Straight line distance for either is over 120 miles. Fortunately, it is very flat country. Overall, the entire FM band was almost full. By contrast, using rabbit ears, I could get a dozen stations at most.
GO OUTSIDE and as high as you safely can, add guy wires just below the rotator if you can, then follow other poster's advice and make sure your array is properly grounded! The key is a good, neighborhood eyesore that you can calibrate to be pointed in just the right direction for the station of the moment. A great rotator will let you set up presets for your favorite stations. Think of it like looking through binoculars - pointing in the wrong direction you do not find what you are looking for.
I hope to buy a new place later this month where I can set up my workbench again and will be getting out that Sony that I bought new in the 70's, recapping it and re-aligning the RF section to see what it can still do. It was not quite the TOL for sound quality, but could DX with the best in its' day - and NO regional blackouts!. That sensiivity is key with the more common low-output-power stations predominent these days.
