Your camera choices are great!
As for getting the most out of medium format, here are a few thoughts:
What are you using for a tripod? Make sure you have sticks and a head that are up to the task.
Consider buying a good handheld meter.
Not on your list - a cable release. Not using one is a sure-fire way to less than sharp pictures if your using slow exposure times.
Get proper lens hoods - and use them. Even modern multi-coated lenses don't like a lot of stray light hitting them.
Shoot a couple of rolls of B&W and make some prints (or scan the negatives) with what you have available before you throw money at the problem.
That's a start...