425W will be enough?
I would ask if it we'll be enough quiet. That 425W up to 300W DC should be quiet (but it depends also on the case: the PSU intake temp matters).
You have to do some math (or buy an energy meter): just for example, a 2500K with P67 and 5450 (and 1 drive) would go for 90-100W DC at around 4GHz (SPCR test, IIRC).
Your 5770 goes for around 80W DC when gaming. So a gross amount of 155-165W DC, plus the two more drives and the PCI cards (another 40W DC when gaming, to be at large?).
But you have a 775, which is less efficient: according to SPCR a P45 and QX9650 with 1 drive and a 9400GT goes for 140W DC. I think your E8400 should absorb a tad less (not to mention the Nvidia pays a +15W premium over the above mentioned 5450).
IMO/IME you should account for around 200-220W DC, currently, when stress-testing (Prime95+FurMark), and therefore something less when gaming (for the 3GHz 125W QX9650, the difference is 15-30W less, depending of the application).
i was thiking more to a 500W
It depends of which card are you looking at: with reference to your 5770, an average 6970 would add about 150W DC to your actual peak DC power consumption (when stress testing), a 6950 would add around 80W DC more, a 6870 maybe 55W DC, a 6850 just 25W DC more. And so on: eventually, if you look for an ASUS Mars II, you would need probably 630W more.
So, IMHO the 425W should handle quietly up to a 6950, at first sight, when stress testing (Prime95+FurMark).
Above it, there's the already pointed out Enermax 87+ 500W at around 105 euros, to be safe and quiet.
But if you're talking about real loads (gaming), then I think the 425W is (or should be) still enough (but for the most powerful video cards, check twice the max required amperage and the number of needed connectors).