Do I need an amplifier
If your phone handset has a relatively quiet volume naturally then you may in fact need an amplifier for corded headset models. Some phone systems volume or loudness is actually quieter than others (LG aria is one). You will also need an amplifier if the room you are in is noisy. An amplifier is anywhere from $100- 150+.
All wireless headset models have built in amplifiers so you can turn up the listening volume well beyond the normal volume offered by the phone system you’re attaching to. If you buy a wireless headset you don’t need to worry.
Sometimes when you add the cost of an amplifier to a corded headset, it can be a smarter decision to get a wireless headset. Not only do you get mobility, excellent sound quality, you also get an amplifier and independent volume controls for both speaking and talking (great if you are a loud talker or perhaps hard of hearing).