Thanks for all the advice. I'm staying at hotels and packing light, I've checked and my total needed capacity seems to be less than 15 L. I've settled on a rear rack and I'm looking at Nashbar bags.
I can't decide if I should get the trunk and panniers (and if so which ones), or just the rear panniers.
Nashbar Waterproof Front Panniers 14L waterproof panniers
Nashbar Rack Trunk 11L trunk
Nashbar Rear Touring Panniers 18.5L panniers
Nashbar Front Touring Panniers 10 L panniers
Possible combinations:
Trunk and 10L pannier ($75, 21L)
Trunk and 14L pannier ($90, 25L)
Trunk and 18.5L pannier ($90, 29.5L, total overkill for this trip)
18.5L panniers alone plus a saddlebag I already have ($60, probably around 19.5L)
Or the 14L pannier + saddlebg might be enough, but there wouldn't be much room to spare.
So, what do you think? Should I go without a trunk? I need to decide soon, we leave on the 29th.
Edit: this is all wrong. The capacity is per pannier.