There is no need to plumb an rodi unit in if you dont want to. Its easier but not necessary. I would go with a full unit and not what you listed in your post.
I went for this system here
http://www.bulkreefsupply.com/brs-4-...tem-75gpd.html from bulk reef supply and they supply a certain attatchment so you can just hook it up to your sink faucet when you want to use it.
Its actually this one here
http://www.bulkreefsupply.com/chrome...ter-valve.html
And then you can just put your waste line in your sink.