T5 usage for low maintenance non co2 setup

[mordrake]

hi all

starting to finalise things for my new tank that will hopefully be setup by end aug.
going for low maintenance non-co2 setup.
as i have never used T5 lights for my planted setups before, i need some input from you guys.

what do you reckon would be enough for a 6ft setup (ht 2.5ft)?
4 x 80W T5 HO? with 2 switches, each operating 2 x 80W.... or individual switches?

not sure whether 2x80W is enough and quite sure 4x80W will give me algae problems since it's a non-co2 setup.
logically it could be 3x80W but would like to hear your views.

thanks

[mordrake]

anyone?