At 100 photos a day (which your average will be to fill a 40Gb hard drive in 21 days) you risk your only memory of the place being through a viewfinder (been there, done that). And if you are talking about 100 'keepers' per day after editing then that is, to me, one hell of a success rate.
From my own experience, I travelled for 2 years through Asia (with a film camera) and shot about 120 films - and that number of RAW files would have all fitted on one 40Gb hard drive. Bu then again, I had to pay the developing charges for all of those so that helped me keep the shoot rate down!
Again, it all comes down to how you prefer to work. Personally, I quite like getting back to the hotel in the evening and reviewing my photoshoot and as I go through them I take the opportunity to delete photos as I go. As I was new to digital at the time, I was also able to learn about my technique each day and (I hope) improve as I went.
But if you prefer to do all editing when you get home, then a non-viewing device is the way to go (100Gb fo £100).
I went through the same dilemma (viewing vs non-viewing) when we went to Canada last year and part of the decision to get the Epson came down to the fact that £350 on a storage device was not expensive compared to the holiday - especially as it will last for years afterwards.
One piece of advice - leave the canmera in the hotel occasionally and enjoy Bali as a place rather than a sequency of photo opportunities! You may regret at the time missing the photo, but you will not regret later on that you saw it without a camera glued to your eye!