Can someone plz help me making a switch to a bigger tank and stocking plans?!?

Ok I havE a 20 gal with glolite tetras, platties 2 male guppies albino cories and 1 male blue neon dwarf gouraMi. In my 40 gal, I have cherry barbs, albino cherry barbs, black neon tetras, gold tetras, cardinal tetras, panda platties guppies and 1 male flamming dwarf gourami. I relize some of these may souls over stocked but I plan on getting a 75 gal tank really soon and here's wat I'm gunna do. I am for sure going to take all the 40 gals fish and water and rock and everything outa it and put it Im my new 75 gal that I'm getting soon. My questions are, could my male flamming dwarf gourami and my male blue neon dwarf gourami go in the 75 gal together at the same time and be civil with eachother? If so, could I add another male at the same time with them? And if they get along, would get like 4-6 female dwarf gouramis make them really agressive towards eachtoher and all the other fish? So I just want to no if 3 male dwarf gouramis, and 4-6 female dwarf gouramis can be together in a 75 gal tank with a bunch of other smaller fish without any agresstion to eachother or my other fish? Could I just take all the 40 gals water and put it in the 75 gal and then add 35 more gallons with tap water, with conditioner in it to fill up the rest and have it be safe to put my fish in it right away? If not, how should I make the switch to my 40 gal to my 75 gal without any fish dying, how should I move the rocks and how should I clean new ones to the point where ican just dump them in cuz I would need to buy more. And does a 200 watt heater sound ok for that tank? Wat size filter? I believe I have a filter that is made for a 55 gal right now and a 150 wat heater that I would be using. So eith the 150 watt heater, wat other watt should I get to keep the water at say 78 degrees F? Please make sure u answer the dwarf gouramis questions cuz that is important to get answered