New build soon need help in the mean time

-- So first off here are thee specs below.

Intel pentium G630
BIOSTAR H61MGC
G.Skill 4GB (1x4GB)
HIS Radeon HD 6670 1GB
Western Digital Caviar Blue 250Gb
GIGABYTE GZ-F5HEB -- (case, it's not the best looking)
Antec VP-450 450w
Samsung DVD burner
ASUS VH202t-P 20" Widescreen LCD Monitor
1) I'm wondering Will I be able to upgrade this to like an i5k processor (once I can afford) and like dual GPU's? Or well I have to get a new MoBo of course i'll upgrade my PSU after upgrading my CPU/GPU my question is will I be able to do it though with the MoBo I have right now and also just do you think this is a bad low-end build? I'll make this into a better build once I can.
2) How will dual GPU help like performance wise. Is there any benchmarks from just solo and dual? Thanks.
3) Is upgrading my GPU to a 7750 worth it? I hear that it's not worth it, can you give me your honest opinion. Thanks

PLEASE READ IT ALL ~FOR ME~

the mobo will support the i5

http://www.biostar.com.tw/app/en/m [...] =547&tab=1