Need advice on pre-built PC.

Hi all, I'm not sure whether if this is the correct thread to post under since I intend to buy a pre-built CPU from one of my local stores in Singapore. Since the parts will be assembled from scratch at the shop, I'm not sure if this counts as a new build or pre-build, but since the shop itself listed this under pre-built systems, I'll post it here but in the event that I have posted in the wrong thread, please forgive me.

As mentioned, I am going to buy a pre-built CPU from one of the local shops, however, I have some queries on the parts that they have selected, the RAM and the GPU.

The CPU in question is the CYMAX Ivy SSD Gaming PC under this link:
http://www.cybermind.com.sg/pdf-upload/pricelists/cyber...
A reference to the computer parts that the store stocks:
http://www.cybermind.com.sg/pdf-upload/pricelists/cyber...

The parts/specs in question just in case the links are down
Processor: Intel Core i5 3570 3.4GHz 6MB
Motherboard: ASUS P8Z77-VLX (Intel Z77) LGA1155 Mainboard
RAM: 16GB (2x8GB) DDR3 1600Mhz CL11 Adata
SSD: OCZ Vertex2 120GB SSD Solid State Drive
HDD: Seagate Barracuda 1TB SATA3 7200rpm HDD (6GB/s)
GPU:ASUS GTX660 DirectCu 2GB PCI-Express x16 Graphics Card
PSU: Silverstone ST60F-ES 600W Power
Disk Drives: ASUS 24X SuperMulti SATA DVDRW Writer (Read & Write DVDs)
Cover: CoolerMaster K280 USB3.0 Chassis

The CPU will be used mainly for both offline (Skyrim, Borderlands 2(depends), Far Cry etc) and online gaming (Guild Wars2 etc.) and watching videos online so I highly doubt that I need a 16GB ram but I do intend to host game servers to play with my friends (Minecraft for example) so I'm not sure if I should change this down to a 8GB ram or stick with what they have selected. As for the GPU, should I stay with the one that they have selected? Or change it up to GTX 660 Ti Direct CU II TOP.
Any help would be appreciated, thanks.