I am thinking of installing Q9550 processor with Cooler Masters V8 cooling solution. I will be over clocking this baby as well *(will be my first time ever) SATA HDD's are a 320 GB & 1TB Seagate 7200rpm & external USB free agent.
Do you think CX400 will be able to cut it, reason why i ask is while searching for this answer the online PSU calculators i ran into all gave me different results varying from 480 - 590... which made my head go
The answer to your question is yes. The Corsair CX400 can power your system.
The online power calculators and video card manufacturers are actually overestimated because the manufacturers are aware people inists on using low budget low quality power supplies of questionable performance and value.