Will This Power My Machine?

I am planning on getting a Corsair CMPSU-400CX 400W ATX12V V2.2 80 Plus Certified. I have heard mixed things about this PSU mostly good, but I am also wondering if it will power my machine, I have been told many things about wattage and I have heard it doesn't matter its mainly about the efficiency.

Heres my specs

Cpu: AMD Athlon 64 X2 7750 Kuma 2.7Ghz AM2+ Dual Core Processor

Mobo: ASUS M3A78-CM Micro ATX Motherboard

Memory: 4gb (2 x 2gb) DDR2 800 GSKILL

GPU: Sapphire Radeon HD 4830 512 MB 256-bit GDDR3

Thanks

it's mainly about the rails within the psu, but to answer your question: yes. it also depends on if you're powering other things like hdds, optical drives, lights, fans. but, that little thing is tough. illharmonics