I have a 250 watt Reef Optix pendant with a Phoenix 14,000K bulb. I like it a lot, although I've only had it for a few days.
I was strongly considering the sundial fixture as well. It's a tough tank to light IMO because I really don't like the look of a 24 inch fixture on a 20 inch tank..
If you're going to be spending the cash on a Sundial 250 watt MH though, I'd seriously consider the ATI Powermodule. It looks sweet on the tank and is only a bit more $.
I think either way you'll be fine.