Finally upgrading to wireless N/Gbe Network

[GullyFoyle]

Here is my home networking setup, all connected to a 10 Mb/s Down, 2 Mb/s Up internet connection from my cable company:

Connection Key ( -> = Wired connection, ~ = wireless connection)

Motorola Surfboard SB5100 Cable Modem -> Vonage Box -> Buffalo Wireless-G High Power Router High Gain Antenna WHR-HP-G54

-> Main PC
-> HTPC
​

~ Buffalo AirStation Turbo G High Power Wireless Ethernet Converter WLI-TX4-G54HP

-> Panasonic Plasma TV
-> Samsung Blue Ray player
​

~ Nintendo Wii (G speed)
~ Nintendo DS (x2)
~ Asus EeePC netbook (N speed)
~ HTC Droid Incredible (G Speed)
~ Iphone 4 (N speed)

Now adding...

~Ipad mini (N speed), Ipod Touch 4th Gen (N speed) (x2)

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I'd like to add a Wireless N router, with Gb Ethernet ports, to maximize the speed to my main PC (wired), and the other wireless N devices.

What I am reading in this forum, is that I should keep the G router for G devices, and add an N router dedicated to N devices. Stick the new router between my Vonage Box and Buffalo WHR-HP-G54.

I know I want to get Simultaneous Dual-Band N. With this hodge-podge of devices, and my base cable connection, would I see any benefit from a router advertised as N900, N750, or anything over N600?