Seeking an answer for my new computer

hi im from Egypt 18 yrs old , how u doing guys ! this is my first question in this forum and i hope i will get a final line over my new computer's components !
just to let you know im not very well experianced in the components thing ive been trying my best for about 7 months and im a gamer mostly ! im using a 17 & 19 LCDs !
first of all the deal was :
Motherboard : GigaByte P45 Ud3L
Processor : Core2Duo Cache 6 2.6
VGA : GigaByte GeForce GT 9400
Power Supply : GigaByte 500v + ( Any gigabyte ps over than 500 v )
Rams : 4 G.B kingston XHyper Rams !
after some researches i found this new pc because many of my europian friends told me that this pc will be so weak so i went so high :
Motherboard : GigaByte Ex-58 EXTREME !
Processor : Intel Core i7 2.6 920 !
VGA : GigaByte GTS 250 !
Power Supply : anything after 600v +
Rams : 6 GB Hyper Kingston Rams !
----- first i want to tell that ive tried to find the EX-58 UD4L or UD5L couldnt find it anywhere :-S also i dont do any overclocking , and i know what will u say : hey u dont need that mobo its too expensive and u got no need for it ! its just because of my curtain budget and the features within this mobo 3 Ways for Video Cards and 6 Ways for DDR3 Rams that would allow me to upgrade only in the mobo without upgrading the whole case !
second of all : ive heard that the Asus Ex-58 Rampage II is wayyyy better than the GigaByte EXTREME so what do u think ?
my questions are : This computer will be super fast in gaming and stuff ? running with no problems ! i know nothing is perfect but im talking about minor issues !
and which is better the GigaByte or the Asus ??
does this pc contain is wrong components or chips that wont work with each other ?
Your conclusion

For gaming, the graphics card is all important. Spend twice as much on the graphics card as you do on the cpu.

Any dual or quad core CPU clocked at 3.0 or better will be sufficient to run the fastest single graphics card you can buy today.

A GTS250 is not a particularly strong card today. The new 5850 is now close to top end. With 17 and 19" monitors, you are not running high resolutions, like 1920x1200 or 2560x1600; you therefore don't need a particularly strong vga card.

All you need for a 5850 is a E8400 @3.0 cpu, 4gb of DDR2-800 and a P45 motherboard. A quality PSU with two 6-pin connectors is all that is required.