Levels honestly aren't doing anything to change the floor space.You could do bin cages for now,just to get them separated and into something which is at least not tiny,but it does not mean that you should simply never think about further upgrading to a larger single level cage such as a square meter cage or even larger if possible!
For now focus on getting them separated though,that is definitely the biggest problem you have at the moment
For wheels Silent Runners are very good,they do have to be ordered online though.They're much safer than any other wheel on the market,as they lack a spindle which is a risk for hamsters with long hair and those who like to climb(especially Chinese hamsters)and the stand is solid which makes it impossible for a hamster to get trapped behind the wheel as long as it is positioned in a safe place.They have a solid front which can help for insecure hamsters as well as make sure hamsters don't go flying off,which would happen with something that has an open front such as a bucket wheel or flying saucer or even a Silent Spinner or comfort wheel!