You may want to pick a different brand. Dynaudio has always had some issues with bass. Every time I've set them up, I always got that one note type of bass. Some people refer to it as a "hump" in the bass. If I had to choose between the 2, I would get the 3.3 over the 1.8.
If you're open to different brands, a pair of Vandersteen Model 2 or 3's would be ideal. The quality of bass if excellent, and they give a lot of placement and correction options. But I'm guessing you live somewhere in Europe so you may not have access to Vandersteen. JM Labs, Audio Physic and Monitor Audio are brands that you probably have access to and you'll have a much easier time getting the bass right.