Lets start off with the filter.
A lot of people, including myself, like the XP series of filters. They are cheap, as compared to other filters, and do a wonderful job. You would need an XP 3. If you have a Petsmart local, you can simply print off the website price and have them match it at the store(if the person at the register doesn't think you can, have then get a manager and it should be taken care of. I have done this numorous times). That will save you a lot of money or just order it online. Petsmart always has free shipping when you purchase more then 50 bucks worth of stuff.
http://www.petsmart.com/product/index.jsp?productId=2752400&cp=2767036.2769231&view=all&fbx=0&fbn=Taxonomy%7CCanister+Filters&f=Taxonomy%2FPET%2F2769128&f=Taxonomy%2FPET%2F2769231&fbc=1&parentPage=family&keepsr=1
For the inline heater, the Hydor is highly recommended:
http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+3743+11369&pcatid=11369
And for the inline diffuser, see this DIY article:
http://www.aquariumadvice.com/forums/showthread.php?t=85573
Now the type and amount of lighting is really up to you. (of coarse)
I recommed getting the Nova HO T-5 setup from the good doctors. Running all four with plants bulbs will put you into the 4 WPG range, so if you want to stick to 3 WPG (not a bad amount at all), I would leave one of the actinic bulbs in it. I would run that one in the socket closest to you when viewing. The fixture comes with two actinic bulbs, so if you wanted 3 WPG you are also going to have to purchase an additional bulb.
Running this fixture also allows you to upgrade in the future. If you run 3 WPG for awhile and decide you want more light, all you have to do is purchase another bulb and you are now running in the 4 WPG range.
http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+3733+12772&pcatid=12772
You can also purchase a coralife 4 X 65 watt fixture, but that is alot of light. In order to drop it down to where you want it, you would have to purchase to 50/50 bulbs. That would put you around 3 WPG and plently of room to increase down the road just like the Nova fixture.
http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+3733+13733&pcatid=13733
http://www.hellolights.com/ also sells fixtures for a reasonable price.
Of course, this is just my recommendation. I have a Coralife lunar fixture running 4 X 65 watt over my 75 gallon tank and love it.
I would also HIGHLY suggest you look into getting a drop checker and some reference solution to monitor your CO2 concentration. A very simple device that shows you how well your CO2 is doing.
I recommend getting that from
http://liquidarthome.net/khstandard .
Just to clear up some things: Actinic bulbs only put out light in the blue spectrum. Plants need more then that, so having actinic bulbs installed in your fixture does little to nothing for the plants and therefore are not counted towards the WPG in your tank.
HTH