I've tried to use a 500 watt inverter with mine, the inverter clicks off as soon as i hit the button (My Ps3 is a new slim model). I've looked high and low in most stores for a high powered one, but alas none.

 

Yeah I tried a 350 but it just clicked off. It didn't work on my 360 but it worked on my ps2

 

If you have a Fry's Electronics close to you then you can get some pretty bigs ones up to 2500 watts. Check out Fry's Home Electronics | Computer Parts & Accessories, Software, Games, TVs, Cameras - Frys.com if you don't have one. The thing is if you use one greater then 400 watts you need to hard wire it into the battery because the sig lighter is to low.

On another note some devices don't like inverters because its a box wave and not a pure sine wave. Not sure if PS3 or xbox is one of those such items.

 

I have a 400w that has battery hookups