The Antec cases are pretty well regarded. I have always been fond of Enlight cases myself though. Right now, I have an Enlight 7230 for over two years without a problem. For my new system I'm getting at the end of the year, I was looking at getting the Enlight 7238 with a 340 watt power supply.
As far as power supplies go, how much you will need depends on how many devices you will be using in your new system. I am planning to have an Athlon XP, one HD, three or four cards (agp video, sound, modem, LAN), a CD-ROM, CD-RW and retail cooling fans in my new system, and I expect 340 W to be enough. If you were going to use more devices or use custom cooling (likely if you are going to overclock), more power might be necessary.
Just stay with well know brands and don't spend more than you want to on a case.