Mix between 4k and 512K sector HDDs

[grendelrt]

I have 2 HD204UI 2TB Drives upstairs (just found out these are now Seagate drives, little pissed about that 4 days past the return window at newegg) and I need to buy a third drive to run raidz. From what I read, the HD204UI is a 512K sector drive, but I was also reading that some people run them with the 4K sector option enabled. So am I better off getting another HD204UI running all at 512K or get something like a WD20EARX and running it with the 2 HD204UIs at 4K? What are possible consequences if the HD204UI doesnt like being run at 4K? I missed this stuff doing research, if I had know I would have just bought 3 WD20EARXs and called it a day.

Edit: Well crap looks like I jumped the gun, newegg just let me RMA the 2 HD204UIs. Guess I will pick up 3 WD20EARXs and run 4K. I will take any advice on this before I buy the drives this time though!