Hi deucebiggss,
I'm the same as you, I ended up buying something because I don't have time to DIY.
My tank is 100 gallons, and with all the lights on I too have 240watts.
I only have 120watts at the moment, tank is doing fine with half the light.
I bought an AM1000.
I think this unit can only just cut it on my 100 gallon, but think, as Tom says, it will be ok on a 75g.
As I ramp up my bubble rate for the warmer weather, this AM1000 is really not going to be able to get me to 30ppm though.
Scott.