Good power supplies compatible with a Micro ATX motherboard?

I'm looking into upgrading my PC. I already decided that I'm going to be purchasing an ATi Radeon HD 4850, but it apparently needs a really good power supply. Most PSUs I see around on sites are ATX, but my motherboard's form factor is Micro ATX. So I'm wondering if there is a good PSU that's over 450 watts and works with Micro ATX motherboards. Or does any ATX PSU work with Micro ATX?