Which psu should i get?

Ok, thats fair - just keep in mind what the ranges are here. A good quality 550-600w is plenty for crossfire. 700w is usually enough for three high end cards. Given increases in component efficiency, its actually pretty difficult to put together a new system that actually NEEDS 1000w. That said, people tend to buy a lot more than they need in the PSU space. That's certainly fine as long as you have a high enough quality unit that it doesn't waste power you aren't using.

You indicated you were looking at platinum models above -- I encourage you to focus on the platinum/gold -- quality is really more important than wattage, particularly if you are planning for the future/long term.

Comment: I have a strong personal bias for Seasonic and Seasonic manufactured units (they make a lot of the highest end PSUs for other companies).