To be honest I'd suggest either a pair of Aquaclear 20 with fluval intake sponges on them or got for a Fluval C3 http://www.petsolutions.com/storefro...erfilters.html
The C3 have all the standard features of the Aquaclear filters but use a vertical basket arangement which keeps you from having to wiggle, wedge and compress the filtration stack just to get it in. They include a basic wet-dry bio-filtration chamber and can use hand-cut filter media and bags readily instead of having to buy cards. As much as I love the bio-wheels, and they DO outperform everything else, if you're concentrating on plants and keeping a reasonable fish load this seems to be the best hang-on-back filter on the market right now. The C series includes the pivoting intake to turn about 80% of the flow back inside the filter so you don't actually lose filtering power by reducing output.
I say the C3 instead of the C2 because you can swing the C3 down to about 70gph for feeding time *(and even lift the pipe up a little bit further and get down to about 25gph) but then rely on the 150gph rate to clear the water after planting or siphoning.
The C3 or a pair of Aquaclear 20s will cost about the same.
For 5 gallon tanks right now I advise the Aquaclear 20s.
**IF** you are planning on overloading the tank, use a bio-wheel. The Emperor280/400 can be output retarded to very low force flow with simple additions and you can get media baskets... they go for about $45.00 or so from Big Al's and the output mods cost me less than $10.00 (see the 280 in this thread: http://www.bettafish.com/showthread.php?t=69826
If you're going to go nearly "OFL" planted you're going to want to use intake sponges and the pair of Aquaclear 20's. Just fill them with sponge, an air-stone and then their bio-nuggets. With lots of long stem plants you get a great deal of very effective filtration and need only have some circulation in the tank. Remember to watch your substrate depth.