Buying a New Desktop (i7 Online Gaming)

Hey there, I am looking to buy a new computer now that my laptop has finally expired (for the record never deal with Dell). The most challenging thing I am looking to use it for is high end gaming. So far the best system I have been able to find has been the following (I have written specs so you need not click):

http://www.newegg.com/Product/Prod [...] 883227132R

Model: Gamer Supreme 985i

General
Processor: Intel Core i7 940(2.93GHz)
Processor Main Features: 64 bit Quad-Core Processor
Memory: 6GB DDR3 1333
Hard Drive: 1TB SATAII
Optical Drive 1: Blu-Ray High Definition DVDRW Combo Drive
Optical Drive 2: 22X DL DVD+/-RW Drive
Graphics: NVIDIA GeForce GTX 285 1GB Video Card
Audio: Realtek High Definition Audio
Ethernet Realtek chips: (10/100/1000Mbps)
Power Supply: 800W
Keyboard: iBUYPOWER USB Deluxe Keyboard
Mouse: iBUYPOWER USB Mouse
Operating System: Windows Vista Home Premium 64-bit
Special Features: Coolermaster HAF Gaming Tower+ Red Lighting
Motherboard
Chipset: Intel X58
CPU
CPU Type: Intel Core i7
Installed Qty: 1
CPU Speed: 940(2.93GHz)
L2 Cache Per CPU: 4 x 256KB
L3 Cache Per CPU: 8MB
CPU Socket Type: LGA 1366
CPU Main Features: 64 bit Quad-Core Processor
Graphics
GPU/VPU Type: NVIDIA GeForce GTX 285
Graphics Interface: PCI Express x16
Memory
Memory Capacity: 6GB DDR3
Memory Speed: DDR3 1333
Memory Spec: 2GB x 3
Memory Slots (Available/Total): 1/4
Maximum Memory Supported: 16GB
Hard Drive
HDD Capacity: 1TB
HDD Interface: SATA II
Optical Drive
Optical Drive Type: BD Combo
Optical Drive Spec: Blu-Ray High Definition DVDRW Combo Drive
Optical Drive 2
Optical Drive 2 Type: DVD±RW
Optical Drive 2 Spec: 22X DL DVD+/-RW Drive
Audio
Audio Chipset: Integrated
Communications
LAN Chipset: Integrated
LAN Speed: 10/100/1000Mbps
Front Panel Ports
Front USB: 4
Front IEEE 1394: 1
Front eSATA: 1
Front Audio Ports: 2
Card Reader: 12-in-1 Media Card Reader/Writer
Back Panel Ports
PS/2: 2
Video Ports: 2 DVI
TV Out 1 x HDTV/S-Video Out
Rear USB: 8
Rear IEEE 1394: 2
RJ45: 1 port
Rear Audio Ports: 6 ports
S/P DIF 1 x coaxial S/PDIF out connector
1 x optical S/PDIF out connector
Expansion
External Bays: 6 x external 5.25" drive bays
1 x external 3.5" drive bay
Internal Bays: 5 x internal 3.5" drive bays
PCI Slots (Available/Total): 2 x PCI-Express x16
1 x PCI-Extpress x4
2 x PCI-Express x1
2 x PCI

Cost: $1417.50

I am flying off to Mallorca this Thursday and won't be back for a few weeks so am waiting before purchasing, firstly incase the price goes down and secondly incase anyone here gives me good enough reasong not to.

I am not all that comfortable in building my own system hence why I have gone this route since I all too often find that parts don't fit, overheat or don't have enough power etc...

I would just like to ask a few questions in relation to this system however.

First of all, how easy would it be for me to stick another GeForce GTX 285 in crossfire with the one alreaddy inserted?
Could I stick DDR3 1600 in with 1333 without a problem or would this not work and if not, can I just remove the 1333 and replace them all with 1600?
Will I suffer any cooling or power problems?
Is there a better system out there for this same price?
Finally I can't remember the name currently but I have heard of a network card which significantly improves connection speed (for use with online gaming which I regularly indulge in) will I be able to hook this up into this and/or is the current setup fine for internet gaming also?

Many thanks,

Tom


p.s. I have no need for a keyboard or mouse or screens I alreaddy have about 10 lots of each. :S