If you have an actual LAN network setup with file sharing or media streaming then yes, I would go with gigabit for your LAN network. If you're only doing internet access, then you are well below the 100mb/s limit of 10/100 ethernet on your current router. If that's the case, then going gigabit wouldn't help you at all.
For internet access, there's no need for gigabit until you were reaching download speeds in the 55-60mb/s range.
EDIT: Another thing to consider is what your end user devices support. If they are only equipped with 10/100mb/s cards then it would be pointless.
Edited by NpaMA, 29 May 2012 - 09:26 PM.