XP1600 or Xp1800?

I'm gonna get the ECS K7s5a (covingering my eyes, waiting for the flying fruit form the audience). Are there any compelling arguments for or against the XP1600, 1700, or 1800?
which should I get?

Gaming system.

I'd go for a Thoroughbred XP1800+. Since the ECS has no multiplier adjustments (that I know of), that chip has the best ability to hit a higher clockspeed with the default multiplier built in.

2.1GHz out of mine on only 1.7V and many others are getting excellent overclocks out of them. Price is hard to beat off Newegg too.

I would get a tbred xp1800 (make sure its a tbred)
It should oc very well and its an excellent value.
1600- I love them, but getting good steppings is no garuntee
1700- why buy when there is only a marginal price diff between it and the 1800.