The Spurs look really good, not great. They're definitely beatable. Phoenix is better than Seattle on the perimeter and has a reliable post presence and a much better point guard. They can win in the paint just as easily as they can win with the three. Marion, Richardson, Stoudemire, and Jim Jackson can all either drive, post, or do a little of both. That's a lot of firepower. The Spurs have plenty of weapons, and better defense, but the Suns are just absolutely overwhelming when they're on, and they're still better than Seattle, even when they're off. I think the Suns win in 6, possibly 7 if Duncan heals really quickly or something.
I would disagree with anybody who thinks Phoenix can't beat Detroit or Miami. I mean, I know it was the regular season and not the playoffs, but Phoenix didn't acquit themselves all that poorly against those two, particularly Miami.