Good choices, I grow all three! Although Echinodorus tennellus is relatively easy to grow I find it to be the most difficult of the three in my tank because of the 24" depth. I wouldn't probably buy an aquarium that tall for a planted tank today knowing what I know now, but it was the size I had and I was determined to make it work.
I am glad I did a lot of research when I started this hobby. I determined that sufficient lighting (including bulb spectrum), fertilizer, and to some degree substrate were three of the keys to success. I bought the AH Supply 1X96 watt kit
, it comes with an excellent reflector. The reflector really gets the light down to the substrate level and the E. tennellus grows with a little reddish color (due to the light intensity) and puts out runners regularly.
Here is a poor quality (sorry) picture of my tank....hope this helps!