Help With Upgrade

[GrandePaw]

I would like to upgrade my current build to something a bit faster. I use the system for browsing, email, video and audio editing and conversion. My granddaughters like to play games (Dishonored, SkyRim, Mass Effect) when they are visiting. 1-2 times a month. Also I plan to add a multi-monitor (3) version of Flight Simulator or X-Plane in the next month or so. My system is currently:

ASUS Motherboard = P7P55D-E
Intel Processor = i5 CPU 760 @ 2.80GHz
Memory = 4ea G.Skill DDR3(PC3-10600) 2048MBytes 667 MHz Model F3-12800CL7-2GBRM
Video = EVGA GeForce GTX 460 SE (going to add same 2nd card for 3rd Monitor)
Storage = Corsair Force GT 120.0 GB = C Drive
Storage = 3 ea WD Black SATA-300 Drives (1000GB, 1500GB and 2000GB)
P/S = Corsair CMPSU-750TX 750-Watt TX Series 80 Plus Certified Power Supply
Optical Drive = iHB212 2
OS = Win 7 Professional 64b

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I would like to upgrade the piece/s of the system that will give me the most bang
for the buck. I need to keep expenses under $500.

Neighbor has suggested CPU to i7 880 as one option.

I would appreciate any comments on the best path to take. System is not
too bad now, Window index = 7.3. Thank you in advance for your time taken to
respond. It is appreciated.

 

[James Godsil]

Here is a list of what you need to upgrade
Motherboard, CPU, RAM, GPU

As for what to upgrade here are some suggestions.
Motherboard: Anything with a socket 1155. An H77 chipset would do you fine in my opinion.
CPU: A third generation Intel Core i5 is what i recommend, but a 2nd gen could work. I.E. an i5-3470.
RAM: 6GB is pretty good today. RAM speed should be 1333MHz.
GPU: This is up to you. I would suggest a GTX 650 as it will not be used much for gaming. You could also go with the last generation and get a GTX 560.