Critique my network! Your advice welcome

Hi folks

I wonder if you can help. Over the last year or so my home network's been expanding a bit and being a bit of a networking novice I'm not sure whether it's particularly efficiently set up. As the diagram in the linked photo shows, I have two NAS drives streaming content over the network, connected to my router. My modem is also connected to my router. i then use a powerline network to connect my main PCs to this, and run backup cycles from them to one of the NAS drives overnight. I'm also using the same network to stream content to my Squeezebox audio player and my Revue video player.

I have a few questions if anyone is able to advise!

1) Am I 'overloading' my network by streaming content, internet, backups etc through one router? Is there any advantage in having a separate router / network for streaming content only? If so, how would this connect with my existing network for file management / content downloading / backups etc.

2) I'm using whatever cat 5 cables I happen to have hanging around the house, nothing special. I'm assuming that's fine, particularly given that a lot of my network is running along powercables?

3) Any suggestions for structuring my network for greater efficiency?

Thanks in advance!

TMW

Anyone got any top tips?

Thanks Riser. I appreciate your advice!