Mac OS X-upgrade help needed

I have just bought a G5 iMac, it is new and unused, but is about 4 years old and therefore has an old operating system on it. It has Panther 10.3 installed(i got a decent discount price on it, this was due to it being on older machine)....

This is my first mac, as i have always used just 'normal' PCs, and the reason i bought the machine is to run music software on it. I got 'Logic' the same day as i got the Mac and now find i can't us it as i need to be running an 'OS' of 10.4 or better.

Can anyone help in general. and also can anyone direct me to where i can download the upgrades required?

Thanx for the help

You'll have to buy 10.4 Tiger, it's not a free upgrade. Or go one better and grab 10.5 Leopard.

Thanx for that

Does it matter which of the ones above i go for... and where would you suggest purchasing it from?? do i need to purchase it from 'apple'

I will only be using the Mac for Logic.

Thanx again

You don't need to buy from Apple, no, but you need to buy the generic disc for either if you don't buy new.
I'd go for Leopard now, especially on the Mac you have.