I disagree with the suggestion to go with an i7, the only difference between the i5 and i7 is that the i7 supports multi threading, which fyi is a type of programming. So in order to benefit from the i7 you must be running something that is written to support multithreading, which is very very nominal amount of things. I personally would highly recommend you research into this further before purchasing an i7.
In my humble opinion 16 GB of ram is to much, if you are looking at an i5 with a decent gpu.
I have 8GB of ram in my current PC, I haven't added any more yet because I have each core over clocked to 4.1mhz and have the case I listed allows the cooling to support this. I have not yet had a core break 60'C with 75% load or RAM usage break 70%, so in my case there really would be no reason for more RAM.
I listed what I used in my build, you really just need to look around, and in depth because you can end up wasting a lot of money on minimal performance return pretty quickly buying upgrades that are of diminishing returns.
For example.. the i5 to i7 upgrade is 100 bucks. You would notice a much better improvement tossing that 100 bucks into a graphics card upgrade.
This is the system I just built in January
CPU: Intel® Core™ i5-2500K 3.30 GHz 6M Intel Smart Cache LGA1155
CASE: CoolerMaster HAF 912 Mid-Tower Gaming Case w/ Adjustable HDD Cage
(Don't forget case fans 120MM)
FAN: CoolerMaster Hyper 212 Evo Gaming Cooling Fan
HDD: 2TB (2TBx1) SATA-III 6.0Gb/s 64MB Cache 7200RPM HDD
SSD: Crucial M4 128GB SSD
MOTHERBOARD: [CrossFireX/SLI] GigaByte Z68X-UD3H-B3 Intel Z68 Chipset DDR3 ATX Mainboard w/ Lucid Virtu Intel Smart Response Technology & 7.1 Dolby Home Theater Audio, GbLAN, USB3.0, 4x SATA-III RAID, 2 Gen2 PCIe, 3 PCIe X1 & 2 PCI
MEMORY: 8GB (4GBx2) DDR3/1600MHz Dual Channel Memory (Kingston HyperX)
POWERSUPPLY: * 850 Watts - Corsair CMPSU-850TXV2 80 Plus Power Supply - Quad SLI Ready
VIDEO: NVIDIA GeForce GTX 560 Ti 1GB 16X PCIe Video Card (EVGA Superclocked)
And yeah you could put this graphics card in crossfire/sli with another one, but again even with just 1 and this set up I have not found a game that stresses this system on max settings.
Hope this helps
Edited by Capital, 30 June 2012 - 03:49 PM.