almost all boards i have are 'all rounders' because i can't really afford to have a lot of boards (not for long

:D) but you just need to think, it's unlikely you'll need a big wave board because it's unlikely that you're a brilliant surfer who can charge. i just get boards for all conditions from 2-6ft really, but have been in slightly bigger stuff with that board as well as smaller surf.
as KS said it would be better to get a board for your ability rather than conditions though because most boards you buy off the shelff in the uk are for average conditions, although you can get bigwave boards. best thing is to get a shaper, be honest and have a perfect board made for you.
type = to suit you
make isn't really important, just be careful what you buy. (KS will reccommend Harmogeddon

) but the best option is to get a custom made one, preferably with thick glassing for longer lasting (& it doesn't really matter if it's a bit heavier because you aren't getting your board free, well not likely)
soooo as for size/type/make go to a shaper and get whats needed