The HD 5450 should have either a VGA/DVI/DP or DVI/HDMI/DP. If you are using either configuration by adding the MST Hub 1-3 or MST 1-4 you can have 5 or 6 displays independent.
Also please note that you have a bandwidth limitation on your HD 5000 series. This series has DP 1.1 specification so make sure what are the resolutions you want to use on the MST Hub. 
In our product page I have detailed a chart under system requirements. Click on this tab to check the supported resolutions as bandwidth increases if you use higher resolutions.
In your case, follow the HBR chart