You know that you want to be 100% invested in stocks. That's a reasonable allocation for many people. But, have you given any prior thought to your allocation within stocks? Rather than picking funds to make an allocation, make an allocation first then try to pick funds to fit it (as closely as possible given the choices).
I am in 86% stocks now. Within that amount, my allocation is this:
US Large Cap Blend - 18.95%
US Large Cap Value - 18.95%
US Small Cap Blend - 9.47%
US Small Cap Value - 9.47%
Foreign Large Cap Blend - 11.58%
Foreign Large Cap Value - 11.58%
Foreign Small Cap Blend - 9.47%
Emerging Markets - 5.27%
REIT - 5.27%
I came up with this after reading (among other things) William Bernstein's The Intelligent Asset Allocator. Ah, the Efficient Frontier.
Now, given that my dough is spread out across Roth IRAs, Rollover IRAs, 401k, and taxable investments, all with different funds available, it's sometimes difficult to hit my target breakdown, but I come pretty close.
Of course, costs play a big role as well.
I guess I'm saying make a list before you go to the store rather than just going shopping and grabbing stuff because it's shiny or cheap.