22 is a good level to start highkeep goblins, just the first 2 rooms though (guard room and lookout room).
HHK Gobs would work for you. But I would say sol a goblins. 2 reasons. If you have a cleric you can get one of the more annoying parts of their epic. The other reasons is the plat. It's massive, need to have a toon that sneaks though. Can sell everything to the goblin merchant with sneak. Otherwise the blocks and bricks get heavy fast.
My vote is for Sol A. All the advantages that sowislife gave are accurate. There are also a couple camps in Sol A that you can tackle as you get towards the mid 20's-30's (level depending on the camp). If you are totally un-twinked then the vendor trash plus drops from named are pretty decent. Plus, Sol A is a little bit more off the beaten path.
I'm a bout the same level as you are, and I plan on hitting up sol a. I have never really done that dungeon, level appropriate or not, so I'm excited to see whats in there. Hope to see ya.
Sol A is harder and if your trio can't stop heals or nukes you will get annoyed. HHK is awfully dull though.
In my notes I have 40 - 50 Unrest basement(until 42), Hill Giants, Spectres, Ice Giants, BW giant fort, and The Hole. 50 - 60 The Hole, TD raptors, Sebilis.