Geodude evolve or power up existing?

Since he is an attacker 71% ivs should work just fine. And yes I would power it up I have a 100% RT/SE golem and he does some work even at lvl 20 I cant wait to power him up.

Is (1) A Golem and (2) and (3) Geodudes? Also, how much candy do you have?

Assuming the level 27 is a Golem, with that moveset and IV, I'd keep it as is and use it as an attacker. At the very least, I would not power it beyond 30 (but I probably wouldn't power it up at all).

As for the Geodudes, I'd say it depends on how much candy you have and what you need the Golems for. If you have plenty of candy to go around and need or really want another Golem, I suppose it can't hurt to evolve another one and hope for a Rock/Rock moveset. If you don't have a lot of candy to use I'd wait at least until the gym rework to see if that changes anything. As it stands, you have a 1/3 chance of getting a Rock/Rock moveset, which isn't great. If there are any moveset changes coming with the gym rework, I can't possibly imagine it getting worse than that, although knowing Niantic and their genius idea of 1/6 odds of Fire/Fire Arcanine, I wouldn't put too much faith in that assumption.

For me, it would come down to this: we are relatively sure that we will see Legendary pokemon soon, maybe within the next few months, and if we do it will likely be the Legendary Birds, all of which share a weakness to Rock, with Articuno and Moltres having a double weakness to Rock. I believe Golem is the only Rock/Rock pokemon you can get with STAB right now (if I'm wrong on that, Golem is at least the best with that moveset potential), so if the Birds are allowed to be placed in Gyms, it's going to be your best counter to them. Assuming the 1/3 odds of Rock/Rock won't get worse, if you have a lot of candy to work with it can't hurt to try getting another one. No one knows what the gym revamp will hold, but if a moveset change swaps one of Golem's Rock charge moves to something else, suddenly you're looking at 1/6 odds.

I blew through 616 Geodude candy yesterday evolving 5 Golem and getting G/G, G/G, R/R, G/R, G/R for movesets. I'm now down to under 300 candy left, no high IV Geodudes, and only one Rock/Rock Golem. I'm really hoping it was the right move, but I'm going to at least hold on to my candy and power up only if the Birds come out. (those two G/G movesets were my best IV Geodudes :)