Busy router, do i need a better one?

Hi,

I'm not hugely experienced in networking so excuse me if any of this is embarrassingly novice.

I have a busy modem/router in the house. Its just the stock one I got from my ISP. We have 3 laptops, 3 smartphones, a couple of consoles and an NAS hooked up to it. I have an android smart TV and a laptop that stream videos from the NAS.

I find when streaming that if there is any other traffic on the router (eg. A torrent downloading/seeding or someone on Xbox live then the stream becomes laborious with lots of buffering.

My question is, is a better router the answer to my issue? If so, any recommendations (complete noob) and if not, what's the cause? I realise internet bandwidth is limited but streaming from an NAS isn't using internet?

Any help is much appreciated.
Thanks