It is not true brother. The Core i5 series CPU is also having their PCI Express Controller (X16) lane inside the processor die.Which means they communicate directly with the Graphics card without the need of motherboard North Bridge. In single GPU gaming performance they can even match the performance of mighty Core i7 processors. The only quad core processor comes near to them is Core2Quad Extreme Q9650, which costs a fortune (almost 35k).
And mandra5, here goes your Corei5 configuration
Core i5 i750 2.66GHz @ 10.5k
Gigabyte GA-P55M-UD2 @ 7.7k
So the total price will be around 18k. Street prce may be little lower. Don't go for the Intel DP55WB P55 @ 6.3k. It is not good for advance users. Overclocking and other tweaking features are really low in this board. Gigabyte board is far better.
I know the hardware architecture my friend...
Yes, the i5 goes away with the NB bottle neck. But again, I have seen a lot of game reviews. The i5 is not 'way' ahead of the Quad 9550 (not extreme). And it does not beat the i7 950. Do remember the i7 has HT and the i5 does not employ that. Also the i5 CPUs have lower cache then the Quads. It is still highly debatable and contestable of which is better i5 or Quad. But I feel the i7 pulls ahead, it is the latest architecture.
The most difference between i5 and Quads would be a few FPS, and this also depends on the game and GPU installed.
But you have mentioned a good price for the OP. He is getting new tech for a cheaper price. The Quad+P55 system would cost him more, with the Quad still being ~12K.
I always suggest the following:
1. New Build: Mid Budget --- i5.
2. New Build: High Budget --- i7.
3. Upgrade a LGA775 -- go for Quad.
Note:
Just speaking in context to Intel. Please ATI guys do not take offense.
(1) and (3) will give almost similar performance, with i5s a shade ahead. Some benchmark number can be seen
here.