IF you know a decent PA will be provided at every gig AND you will have a way of monitoring then you don't need an amp. Some might say that's a big if, but not really. In my case, I do own an amp but have not used it in about 7 years, except when I've done a couple of sub gigs. I used to be in a band where one guy brought his PA to every gig and it had subwoofers and I could plug my IEM's into it, so never needed an amp. Then I got into another band where I provided the PA and I always bring a subwoofer so I never need an amp.
BUT, if you are planning on doing any sub work, then you do need an amp because you never know what the other guys will have for a PA (even if they claim to have a great PA). For sub work I always bring an amp, even if it ends up just sitting in the car.
BUT, if you are planning on doing any sub work, then you do need an amp because you never know what the other guys will have for a PA (even if they claim to have a great PA). For sub work I always bring an amp, even if it ends up just sitting in the car.