Motherboard : gigabyte GA-M68MT-S2
Processor : AMD Phenom ii x6 1045T
Hard drive : 1TB HDD
Ram : 4gb
PSU : 200W
Yes, you can. Need increase ram to 8 gb and ofc new PSU.
What cards ? max 3 on this mobo, so it can be, for example 3 1080.
You do not need 8gb ram for 2-3 cards, just a waste of money.