It depends on you buddy, its not safe to use that generic PSU, we never know how much it is actually capable of giving, it can probably run the rig, but cant say for how long and how well, better, get a good quality PSU and forget about it.
For starters, send the pic of the side of the PSU where it shows all the voltages and the currents.
@pegasus: A 550VX is still an overkill, even with 30A on 12V, he will still have plenty of juice left for safety, my point being, we should suggest the cheapest one (price not quality) that would make the cut, rather than planning for something that may not happen. But as you said, 450VX is a good choice for existing setup with plenty of room, 550VX in case he wants a much better GPU.
I dont know how much the 450VX costs now, but another good option would be a Seasonic 380W PSU (dunno exact model number), that costs about Rs2800, will easily Power a Quad Core (normal OC,nothing extreme) + HD 5770.
Peace
