On the other hand, if this is your first low tech set up, I'd go with something simplier. While dwarf hairgrass heteranthera zosterifolia can be grown in a low tech tank, they are a couple of the more difficult ones.
I don't know anything about the lights your using but 3+ watts a gallon with only excel is pushing it. You'll have to dose a lot and do lots of water changes and you get higher and higher maintance. And will probably be fighting algae.
The eco is good stuff. But if you want sucess the first time out, I keep the lighting 2-2 1/2 watts and choose plants that do well for that amount of light. Then you can dose a couple times a week or when you feel you need it. Lileaopsis could make a good sub for the hair grass. I also have it my potting soil tank and it's very pretty and does well. And Sags go crazy in my 180 and I have similar water parameters as yours.
Good luck and keep us posted,