2c-e hydrochloride is the "usual" 2c-e (for us, anyways). Without the hydrochloride, the 2c-e would be in it's freebase form. 2c-e freebase is an oil, not crystals or powder like you normally see it. It's also not water soluble in this state. The dosages you see on erowid and around the internet are already based around the fact that it is in the hcl form. I'll spare the technical details, but if you're interested to learn more you could check out this link: http://en.wikipedia.org/wiki/Hydrochloride
Also the main difference, in my opinion at least, from hcl and freebase is that you can't smoke hcl. There are also small dose differences, but I don't think they are that different.
It just like cocaine... cocaine usually comes a HCL which makes it snortable or shootable, you need to add a base to HCL to make it smoke about, just like baking soda is added to cocaine to great Crack, a smokeable form... I pretty positive you can eat most HCL but sometimes it needs something extra to be absorbed into your stomach...? hopefully I am not that far off...
The HCL form is soluble in water, which is why cocaine hcl is insuffliated or injected. Since it is water soluble, it is easily absorbed across the mucous membrane in the nose and into the blood stream. Cocaine freebase would not absorb in the same fashion because it is not water soluble. The reason freebase cocaine is used for smoking is because the tempature at which it vaporizes is much lower than the tempature at which it is destroyed from heat. This is not true for cocaine hcl, the tempatures are much closer together, so a lot of the cocaine hcl is destroyed if you try to smoke/vaporize it. This is not always true for every chemical, so some chemicals can be vaporized in their hcl form. Also, your stomach contains hydrochloric acid, so even if you swallow a chemical in its freebase form, it is essentially converted to the hcl in your stomach. This is needed to allow the chemical to be quickly absorbed through the stomach lining and into the blood stream.