What amp is loud enough?

I am looking into new amps and wanted one that would be loud enough to play with my cousins and my brothers drums. I was wondering how many watts would be enough to be heard over the drums. I was thinking a 30 watt behringer or a peavey vypyr but I want something that is not to big and to loud for my house but loud enough to play with my brother in our room and stuff. Any more than 250 dollars is not in my price range. I like rock ACDC, GnR, and Poison but I also like to try some blues and metal. I need a versatile loud amp. Links and Suggestions are good, Thanks.