I wouldn't get a Whisper... they're really pretty lousy filter filters. I would also ditch the air pump, they're not really needed, unless you absolutely _have_ to have that treasure chest that opens and closes in your tank....
I would recommend getting two HoB style power filters. Maybe two Penguin 350s, or a 350 and an Aquaclear 70. If you place them on the back of the aquarium, at either end, you'll get excellent circulation, and if one dies, it'll buy you some time to get it replaced.
Same thing goes for heaters... Run two smaller heater instead of one big one. A lot of people like Visi-therms, but I've had good luck with pretty much all fully submersible heaters. As long as the tank the room is in isn't too cold, you should be fine with two 200W heaters. If the room does get cold (some people (like me) turn their heat down to the mid-50's overnight), I would recommend getting two 250W heaters
Just a rule of thumb, you're never going to have too much filtration on a tank. A filter rated for a 60 gallon tank is never going to be enough for a 75. I would never even run it as the sole filter on a 55.
Almost all my tanks have two forms of filtration and two heaters. The peace of mind is well worth the slight increase in cost of buying two smaller, rather than one larger.
Just my $0.02, hope it helps.
~JW