Oooh. I like the linkable feature. As it is, you'd have 48w of light for a 29gal, so that's about upper low to medium light. If you ever linked it and got a second, you'd have medium to bright light and be able to grow some really amazing plants. But your algae might go nuts.
Same wattage as the first but cheaper. But no expandability options. Hmm. But cheaper is nice!
That's some nice wattage. 62w. But you'd need to replace the actinic blue bulb with a daylight or pink bulb. Actinic is for corals. That price is unreal. Does Big Al's ship to the US?
Wow. Even better wattage. Does it come with mounting legs though? If not, it might run very hot sitting on top of a glass canopy, which in turn will raise the temp of the tank. All of those high wattage T5-HO will run warm, though.
My advice is go for the last one if it has mounting legs. That will give you almost 3w per gallon which is pretty bright. You might even be able to grow hairgrass as a carpet with light like that. But you'll want to make sure the tank is pretty heavily planted so it sucks up the light or the algae could go crazy.
Dang, those are some good deals.