My two bobs worth is that 165mm cranks are already the longest that I would recommend for you based on your inseam and that going longer is going to loose you more than you could possibly gain for a bit of bling.

Longer cranks will be harder to spin at high cadences and longer cranks will make getting into an aerodynamic tuck more difficult. If you are going to change anything I would be selling the 170mm cranks and finding another 165mm set.

Anthony