There are several places where you could buy amplifiers however the best way for you to proceed when looking for amplifiers would be by browsing through classifieds as well as promotional sections of different websites to see if they have any amplifiers for sale. The reason that this step is recommended is because you will be able to save money by going for your most desired amplifiers without having to pay normal retail prices for them.
If you simply go ahead and only look at those websites that have amplifiers without focusing upon discounts then you may not be able to save any money as you might as well find yourself having spent a lot more than what would even be considered to be acceptable.
That does not however mean that you should be going for an amplifier that does not have all of the features that you may have been after as the first thing that you should be looking at is the feature set that the amplifier may come with. It may therefore be a good idea to look for amplifiers for sale just to get an idea on what brands you could be purchasing before you can carry further research out and do some reading about individual brands and models so you can easily decide whether you should be going for it.