Sure, all these products will take care of your nitrate, but they won't take care of the underlying cause(s). Nitrate in itself is relitively non-toxic, but it's a good indicator of dissolved organic coumpounds (DOC's), wich is really why you should be concerned about nitrate in the first place. All the nitrate removing flter media and chemicals only remove the nitrate - not the DOC's. So while you may end up with a low level of nitrate via using these products, you will still have the DOC's wich they shoul dbe indicating, but they aren't now that you removed the nitrate (so basically using nitrate removing products is more trouble than it's worth).
Nitrate is cuased by the creatures living in your system - fish, corals, shrimps, crabs, ect. Elevated levels of nitrate is cuased by imbalances within your system - too many fish or too small a tank for the given fish population, some filtration methods and a new(<3 months) tank are just some examples of the cuases for elevated nitrates (and DOC's).
If you want to lower your nitrate and the DOC's it indicates, you need to treat the imbalance(s). Removing fish(espescially fish wich are inapropriate for the tank) or upgrading to a larger volume of water, adding a skimmer or upgrading to a more effecient or effective skimmer (this removes the DOC's directly from the water coloum), increasing water changes or reconsidering/changing your filtration method are IMO the best ways to treat this problem (listed in no particular order). The addition of macro algaes, deep sand beds or more live/base rock can help, but I feel that that would be leaning more towards treating the syptoms and not the cause(s).
And no, I have never and will never use chemical filtration such as seachem's "de nitrate", becuase they merely treat the symptoms and not the cause.