Doing some research last night, and came across A123's Developers Kit, which is really quite exciting because now I know I can get small quantities of their batteries even if I don't find sponsorship from them, all ready to put into my system. The DK comes with 6 of these 3.3V, 2.3 Ahr beauties for $129, tabbed and ready for assembly into packs. But since 6 is not an even multiple of 4, two developers kits are $220. A 3x4-battery series, this would result in a 13.2 V, 27.6 Ahr pack, or roughly 360 Whr at around 860 g (1.8 lbs). 360 Whr is enough to run my intended 30 W system for 12 hours... and it will be well, well worth it.

Can't wait to charge up ^_^