iPod How to copy music from old to new iPod?

I'm looking to buy a new iPod Touch as I've pretty much maxed my 8gb Nano 6th Gen.

Thing is, I've had the Nano for 2 years now and during that time I've been through a couple of PCs.

I always set my iPod to manually update, this means that alot of the music that is on my iPod is not saved on my latest PC's iTunes library.

Is there a quick way of copying all the music on my Nano to iTunes so I can sync it to the new iPod?

Well that's a bummer then

Half my music comes from various other sources (7digital, Amazon, Tesco etc.) so it makes the process all the more longer.

I've used a software called pod2pc before but that's a long process also.