From what I have read if you live in a RF rich area i.e. a larger City it will probably make things worse. But if you live in a area such as I do, out in the country with the nearest cities 25+ miles away, it means hearing or not hearing (and even then the "cities" are small 25K - 50K people. The closest "big" city is Topeka KS about 65 miles away, and out of range with any antenna or amp).
Even so, when my little local town PD transmits it will usually bleed all over with the amp and I can hear them on just about any VHF freq I have programmed. It is not a problem as they can go hours without a single transmission.
Of course a good antenna and good cable are the first thing to get.....
I use two, a Hamtronics on my base Antennex 800 antenna and a GRE Super AMP when mobile. However, as Fredg said they are not for everyone. I live in the country with no major RF interference. I seldom use the GRE Superamp when mobile because of the RF interference.
It all depends on your needs and the type of monitoring enviroment that you live in. I think that fact has been very well stated. Having said that, it is Hamfest season. If you can find one, GRE used to make a desk top amplifier named the "super amplifier 3001". I got mine at a Hamfest for $10 and it looks new. It is a stand alone desktop unit that has the same characteristics that the hand held one has but is better configuered for desktop use. Same variable 0-20 db gain adjustable knob, on/bypass switch. I use it upstairs in my master bedroom on my nightstand where there are 2 scanners that I cannot run an outside line to. Works for me! Here is a picture I found on the internet, take a look:
You've already gotten some great advice here but I'll throw in my 2 cents as well.
I use the GRE Super Amp 3001 and consider it to be one of the best pieces of equipment in my shack. I have 3 BC-895's and 2 BC-780's all hooked into it (lots of short custom-made coax lines along with a lot of right-angle and T-adapter BNC's :wink: ).
I live about 25-30 miles northwest of NYC, in northern NJ. My house is located in a valley. Using the supplied back-of-set antennas would only get me my local FD/PD/EMS units. I was able to put a scanner antenna on my old TV antenna mast and that made a world of difference in reception. I was able to hear most of the towns in my immediate area. Then I got the amp and I was really astounded. The amp allowed me to go from hearing what was in a 15-20 mile radius to basically the upper third of NJ and southern NY, as well as NYC and western Long Island, NY.
Location of your antenna/radio is most definitely a factor. My buddy, who lives in the same town as I do but on the side of a hill, borrowed the amp and found out it overloaded his radio. Because of his higher location, even being in the shadow of a hill, he only needed the roof-mounted antenna to hear everything I could hear.
Many, many thank you's to everyone who responded to my question and offered their advice. I guess you guys made my decision easier. I'll be ordering one this week after looking around for a good deal.