Presuming connectors, voltage etc are the same the wattage increase won't be a problem at all.
From: http://ask-leo.com/is_it_safe_to_install_a_higher_wattage_power_supply_in_my_computer.html
I've heard a concern that a high-wattage power supply can somehow "force" the power onto the computer, causing overheating and burnout. Nothing could be further from the truth. A power supply supplies power in response to need; it doesn't push power anywhere. If your computer only needs 100 watts, then a 500 watt power supply will only supply 100 watts. Why have a 500 watt power supply? For "peak" usage (sometimes hardware will require sudden "bursts" of power, such as at start up or under high load) and for future expansion.
It's better to have too much power than too little