N Router with G adapter how much you would lose?

Computer Type: PC/Desktop
System Manufacturer/Model Number: Custom Build
OS: Microsoft Windows 7 Ultimate 64 bits 7601 Multiprocessor Free Service Pack 1
CPU: Intel(R) Core(TM) i7-3770K CPU @ 3.50GHz
Motherboard: ASUSTeK Computer INC. P8Z68-V PRO GEN3
Memory: 8.00 GB
Graphics Card: NVIDIA GeForce GTX 670
Sound Card: Omega Striker
Monitor(s) Displays: Viewsonic vx2250wm
Screen Resolution: 1920 x 1080 x 32 bits (4294967296 colors) @ 60 Hz
PSU: Corsair Gold Series AX850
Case: nvidia 690 advanced II
Cooling: Air
Hard Drives: V9CPETXT Seagate 1TB.