Enhance scoops out the mids while "apparently" bossting the lows and highs at the same time. (Good for dialing out punch in my opinion)
Semi-parametric means you can select the frequency you want to boost or cut with the +/- knob.
(A fully parametric EQ gives you a third knob which allows you to select how wide an area surrounding the selected frequency point you also want to affect. This control is referred to as the "Q" . with this control you can specify a very narrow frequency range to be affected or a very wide freq range.)
A semi parametric EQ is very useful and makes Eden amps very ideal when you desire to tweak your tone.
Eden uses semi-parametric EQ sections and makes the "Q" decision for you by engineering it into the EQ circuit. (abuse of a fully parametric EQ in the hands of the novice can do much to degrade the sound of a bass)
Kinda like giving a 17 year old a Maserati.