Stupid question, but is the neo-gui-rpx wallet for RPX only? So, only need to transfer the NEO you wish to invest in RPX? Or is it a replacement of the old wallet?
If you want to participate in the RPX ICO you need to have your NEO in the 'neo-gui-rpx' wallet as it has extra options needed for the ICO, more info here
https://coin.red-pulse.com/neo-gui-guide .
If you don't want to participate in the ICO you can keep using the 'neo-gui' wallet.
I have both wallets working, the RPX one for the ICO and the 'neo-gui' for the rest of my NEO.