I have a 3.5mm to RC which works with my old amp, not sure what coax and optical mean in regards to that. Will that work or do I need something different?
I should add that besides the lime green line out port at the back of my pc is an orange C/SUB , a black REAR port and a s/pdif which I believe is a toslink connector. Looking online everyone says to use the s/pdif port. Should I purchase a toslink to RCA wire or can I use any of the other ports with the wire I already own?
You're right, that's the optical output from your PC and it will do nicely.
At the moment the soundcard in the PC is doing the digital to analogue conversion (DAC) and sending analogue out of the 3.5mm line out socket.
In future you would send optical digital from the PC, along the glass (or plastic) fibre of a Toslink cable, into one of the 2 optical inputs on the Marantz, where its DAC will then do the necessary conversion to analogue.
This type of lead is what you need. Go for a cheaper one if you want. Gold plating (24k or otherwise) is totally unnecessary. Just choose one that's not hair thin, so that you've got some mechanical strength.
The link below takes you to the 1 metre version, but you'll see other lengths listed:
Free delivery and returns on eligible orders. Buy Cable Mountain 1m Premium Toslink Fibre Optic Digital Audio Optical SPDIF Cable with Metal Case and 24k Gold Plated Pins. at Amazon UK.
www.amazon.co.uk
Bottom line....you will never have heard your PC's music sounding so good
PS: You might wanna get a couple of leads, your TVs likely to have a digital out - which could go into the Marantz's 2nd optical input.