Also a greatly amplified signal can result in overloads to the front end of the scanner. The amplifier (really a preamp) amplifies any signal, and that includes noise. If the signal is already strong with the regular ducky antenna it will likely overload the scanner's front end and cause problems. Of course you can fix that by attenuating the preamp signal with the knob, but it could be a nuisance if you are constantly having to readjust it.
Overall though, I'd go for a better antenna. I bought a Watson 8 in. long "regular gainer" antenna and it makes a big difference when the scanner is on the road with me. You can get wide band antennas with proper radials, and if you stick one high in the air with a length of coax to your scanner while it is in the house, that will probably do more for you than any preamp. Of course the neighbours might object to a high tower in your backyard or on the roof.
My neighbours did so I moved my 8 foot high commercial wide band antenna into my upstairs bedroom and connected it to my scanner downstairs with 50 feet of 75 ohm TV cable type coax with some adaptors needed to fit the BNC jack on the scanner. The theoretical impedance mismatch seems to make little practical difference and I can scan a lot more systems. The repeater on Mount Seymour near Vancouver is about 70 miles from my location in Victoria B.C. and the big antenna gives me a five bar signal with no extra preamp required.
But even the 8" Watson ducky makes a big difference when I'm on the move and it was only thirty bucks. You can probably get better ones cheaper depending on where you live. The reviews for the Wilson I found on line were not terribly complimentary but it was cheap and it works fine for me. Much better than the stock 4 inch ducky.