The two basic specs are noise figure and gain. Noise figure is the degradation in signal-to-noise ratio in dB due to amplification. Typically the lower the noise figure, the moe expensive the electronics are. Gain is the increase in amplitude of a given signal input in dB. Solid Signal has an article you can read -
http://www.solidsignal.com/p/?p=3561
You can compare the specs and share them with us. Perhaps buy a few of the ones that best fit your needs and give them a try. Or if you just want to try an amplifier without more effort, ADTech gave you an excellent suggestion for testing the utility (or futility) of adding an amplifier.