You definitely DON'T want to plug 230V into it. The silkscreen writing on the board is referring to the fuse, which is rated for 230V. There is a PSU mod for KAGA 110V powersupplies to get it to work with 230V, but it involves soldering in resistors and replacing a capacitor. Not all Japanese Dreamcasts have the same powersupply though, I recently bought my very first DC, a Japanese model, and I'm going to have to order parts to build my own PSU because this one is not moddable.
You can also preorder the DreamPSU, or DIY a powersupply with a PicoPSU, both of which will allow you to power it with a 12V DC power supply.