The links given by you are not working.
This build that I give makes some compromises in terms of overclocking,and dual GPU setup, but upgrades GPU and Monitor. It includes a 23" monitor as well.
CPU & Motherboard : $262-i5-2400 & Biostar H61MU3
(Great processor , and decent motherboard)
RAM : $35- GSkill NS 2X 2GB
Power Supply: $55- Antec NEO ECO 520
(insufficient if a second card is added in future)
Graphic Card : $240- MSI Twin Frozr II 560Ti
(Great Card for its price )
Monitor: $160- Acer 23" LED Backlit 1920X1080
HDD: $40- Seagate Barracuda 500GB
Case: $35- Sentley Black
Optical Drive : $19- LiteOn
Total(Excluding Rebates) : 846 USD
Rebates : 20 USD
If this goes overbudget . possible downgrades include :
1. Get Acer 21.5" LED Backlit worth $130
. Save $30.
2. Drop the card to Sapphire Radeon 6870 worth $175
. Save $65.
These downgrades would allow you to get i5-2500K and a SLI/crossfire capable motherboard (like i5 2500K and MSI p67 G45 worth $325
Hope that helps