Front Disk Size?

Hi..

Im changing my breaks again.. didn't get used with the Hopes as they are not in the European way..:8)

Now.. i have to get one adaptor from the front rotor and a new disk too. I like the 203mm in the front well, but don't know if is too big only for XC ride.

So there is the question, with size from the front rotor to go? keep the 203mm or get a 185mm.. or get back my old 160mm?

I'll be running some Hayes nine now.. as i can put it in either side of the bars
160mm is fine for an xc bike, 203mm would be way too big and probably void the warrenty on the bike if it still has one and it's an xc bike.
Now thats a fine Goober question if ever there was one !! The European way..thats the love between Oz and Luke isn't it ?