Dependent Drop-Downs

Hello,

In the attached spreadsheet, I am trying to set up drop-downs in the yellow-shaded cells that only show the relevant SKU names for the specified Device Model and SKU Category. For example, the user would select "Model-100" in cell B2, after which cell B4 would contain a drop-down list consisting only of cells C11-C13 ("System 1", "Bundle 1", "Bundle 2"). I am familiar with creating basic dependent drop-down lists, but for some reason the multi-tiered nature and special characters are making this not work for me. Can someone help with this? Thanks!