I have a question for you. In none of your posts do you say you need a wireless router. Yet the G and N you talk about are short for 802.11G and 802.11N. These are both wireless protocols. So are you going to connect to your router with a wired, or wireless connection?
First let's assume wired. A 100 Mbit/sec (100Base-T) connection will make the internet connection the slow point and that is your goal. So you'd need a router that also has at least 1 100Base-T port. You also need an ethernet adapter in your PC that supports 100Base-T. Most modern PCs already have that.
Now let's assume that you are going to connect to the router via a wireless connection. Here are the theoretical maximum transfer rates of standard G and N protocols:
G: 54 Mbit/sec
N: >100 Mbit/sec
So to get the maximum out of your PC, you'll have to use 802.11N. No matter which wireless protocol you decide to use, again you will have to be sure that your PC's wireless adapter will support that protocol.
For more information about wireless protocols and their performance, check out this link.
HTH rather than confuses.