well. if you have another line 6 product that you can connect to your computer. and it has the vdi connector in it and the cable tothe guitar then all you need is the software. so what it is is this. the software has been upgraded a few times..
if you buy the guitar and have no connector to the computer what your really paying for is the workbench connectivity hardware consisting of two cables and a connector/ adapter box. thats what i use and it works fine. when you buy this package the software will be the old software and youll have to download the upgrade anyhow.
but without a connection from the guitar to the computer.. the free software is useless.
me id get the jtv first.. you may like it just as it is. then if you need the software/hardware package go from there. .
i had a 300 and it was good as it came. i did make a couple of tweaks but nothing substantial.
and the jtv is far beyond that 300.