While the poster above is correct, I don't think there's a compelling reason to replace the power supply if it's working for you and you aren't planning to overclock or install a higher-draw videocard. Your new CPU actually has lower power usage than your current one, down to 84W from 95W.
I'd recommend at least a 600-650W power supply, not because you actually need that much for most systems but because for many brands build quality drops off significantly below this mark. For the last 1-2 years power supplies below 500W have had significantly higher measured failure rates for this reason, and I would expect that trend to start to extend to <600W power supplies soon if it has not already. Keep in mind that you want your power supply to significantly exceed the maximum load you expect your system could ever draw, both for headroom and because most power supplies tend to ramp up in noise past around 50%, and usually get extremely loud beyond ~80% load. Power quality also declines similarly, though any decent quality model should provide stable power throughout its operating range. Cheaper models will not, and may even damage attached hardware at high load levels. This is why it's so important to get a good quality power supply for high-draw systems, not just one with a high wattage rating.
When considering power supplies, the first thing to look at is that it comes from a trustworthy brand. This is because if you are buying from a no-name brand the specs on the side of the box are simply lies. Any power supply you consider should have at least 80+ Bronze efficiency, Active Power Factor Correction, and only a single +12V rail. Models missing these features are obsolete and usually not compatible with modern hardware.
Historical note: Amps on the +12V rail aren't a particularly important stat to worry about anymore. That was a big issue back when obsolete power supplies that had most of their capacity on the +5V rail were common, so you had to check that a power supply you were considering did have the right balance. Today all power supplies have the vast majority of their capacity on the +12V rail, and typically have only a single strong +12V rail. The technical reason for the change is that back in the day power supplies were essentially designed to have separate components converting from AC to each voltage produced, such as +12V and +5V. Today power supplies convert from AC to +12V DC, which is then converted to the other DC voltages. This means that the power supply must be capable of supplying the entire combined load of all rails from the +12V since that is where they are fed from, so you know it has a strong +12V rail.
This got a bit long but hopefully its helpful