Hi ggoetzii,
First of all … congratulations on your new mattress 
You can read a little more about adjustable beds in post #3 here (and the adjustable bed thread it links to). For most people they would be “preferences” but there are also some people with certain conditions or circumstances where they would be more “needs” where they can help with some health conditions as well.
For back sleepers that are prone to lower back pain on their mattress … raising the lower part of the mattress a few inches can help to flatten the lumbar curve and can reduce the tension and stress on their back and can reduce lower back pain (similar to putting a pillow under the knees). Raising the legs above the heart can also help with some circulatory issues. There are also some benefits that can be helped with raising the head of the bed (such as acid reflux or snoring).
If an adjustable bed would only be worth it to you if you “need” it then I would tend to try your new mattress first to see how it works for you without it unless of course you already know that you have health or back pain issues that would clearly benefit from the adjustable bed regardless of the suitability of your mattress.
Our adjustable bed was a preference (and both of us spend a lot of time side sleeping where of course elevating the bed except for a very small amount wouldn’t be appropriate) but hopefully some of the other members that have benefited from an adjustable bed will see your post and share their experience as well.
Phoenix