Ask a Bowman Thread.

Got my new shoes today n_n Raised my range by 100.
Keep or cube em?

Are you trying to make them your end-game shoes or just use them temporarily? If you want them to be your end-games shoes, I would sell them and look for a 3 bonus shoe and then cube the shoe.

If you are the latter, then it depends on how much you are willing to spend on cubes. A 3% dex bonus easily beats a static 15 dex bonus, but since stats are randomized, it may take a few cubes to get the desired stat.