Yes, absolutely assemble the gear and then decide how to pack it. Volume may be a greater concern than weight. We put everything made of fabric in waterproof compression sacks, like these:
http://www.rei.com/search?query=compression+sacks

We used the Sea to Summit. One 14L held our tent and sleeping bag. The others were 6L.

A 1-2 day resupply at grocery stores doesn't add too much weight or volume. Way to go. Eat fruit, better than Clif bars. Day-old coffee cake is great. Makes a wonderful no-cook breakfast, then up the road.