for PSU, Corsair 650 watt would be a good choice. OCZ/PC Power & Cooling, Antec, Enermax, Seasonic, are good brands for PSU too. I like the Logitech G15/G11 for keyboards, and the G9 Mouse is my new favorite. I've used Razer mice for the past 5 years or so, and they're good too, but I like the G9 much more now.
A Corsair 750TX PSU would give you enough headroom to add another 4890 in crossfire down the road.
I'll let someone else recommend a keyboard/mouse.
definitely bigger PSU if you like to add crossfire. There are other gaming mice and keyboards out there that are fine too.. Saitek makes some good ones, and I think microsoft made a sidewinder keyboard not too long ago, but I always thought those other brands never grasped the productivity aspect of peripherals as well. Logitech addresses both I think.