The Lian Li TU150 doesn’t come with any dust filter at the bottom. As the bottom fan is responsible for the intake of air, it will be dusty.
For casing, I am looking at Lian Li TU150 in black. It is a mini-ITX chassis that supports four 120mm fans — two at the bottom, one in front, and one at the back.
They say Noctua has the best casing fans and hence it is expensive. It cost about US$29.90 (S$42) each.