I was considering bringing my American systems to Europe. Is it true that I would need a transformer because the volts are different. I already have the adaptor for the wall socket so I just need to know about the voltage issues.
Yes. You will need something like this http://cgi.ebay.ie/100W-Step-Down-Transformer-240V-to-110V-Converter_W0QQitemZ280075663843QQihZ018QQcategoryZ294QQrdZ1QQcmdZViewItem
Make sure you get a step down transformer with a decent power output (measured in Watts). If you plan to play a PS2/XBox then I'd get one measured at 150W, if you're wanting to play on the PS3/XB360 then it gets a fair bit more expensive. My advice would be to order one at somewhere like Maplin and get it delivered to the place you are going to be staying at because they weigh a ton! I think the slimline PS2 works on US and European voltages, but you'll need to check that out. If it does then it will usually have 50hz/60hz 110/230V printed on it somewhere, or it will tell you in the PS2 instruction booklet. In that case you'd just need a plug socket adapter (the plugs are different over there)
I bought a 240V-110V, 200W stepdown for 19€ yesterday for my USA Xbox and works fine (I haven't played a lot with it).
XBox or XBox360? The original XBox is fine on that stepdown but the higher power requirements of new systems makes using an under rated stepdown potentially dangerous.
With the more expensive step-downs, you may be better off buying a European PSU. A European 360 PSU should work on a US 360. You'll also need a TV capable of displaying NTSC 60hz. Most reasonably modern ones should be fine. You could say any with a SCART, but a lot of early SCART-capable TVs were unable to. Something up to 5 years old, it should work. Don't forget, with many machines you won't be able to play European software without modifying the console, if at all. Are you staying in Europe? If so, you might want to consider selling yours there, and re-buying over here.... although that may not work out for you economically!