buying cheap sound bar will only downgrade, go for passive book shelf.

Firstly, 8 inches speaker is not easy to play well, space is very important. Do you have speaker stand? It is not something that will sound good if you just put in on a table. If the positioning is not in order, the sound would be muddy, separation, sound stage won't be good as well.
You should at least separate the left right speaker to 2 meters. The position from yourself to the speaker should be further as well. There are a lot of ways on positioning the speaker which you can find online. The simplest way is to form an equal side triangle.

After positioning the speaker, you can try to check out what do you want to improve.
Another thing that you can consider upgrading would be your DAC. Studio 8 is a quite decent speaker for the price. But DAC should be good as well since it's the first point providing sound signal to the speaker. It determines the quality of the sound signal that the speaker will receive.