So far I've found boilers to work really well... boiler > turbine for eu or boilers > industrial engine for mj.
rotors only last 41 hours, but it's a meezly 50 steel (iron > blast furnace) to replenish. Your quarries or manual mining should find a shit ton of iron in 41 hours.
Converting is a bit of a waste when you can directly create it fairly cheaply.
For quarries, the absolute best thing I've found is make MJ batteries (depending on the size of the quarry, you'll need more) - charge them up and setup your quarry. A normal sized quarry needs 1 and 1/3 batteries.