If I'm installing this in a basement, should I still use some kind of subfloor?

Hello Riley and thank you for your question. The Style Selections Luxury Vinyl Plank flooring is a waterproof product and can be installed in the basement. One requirement would be to install a 6mil polyethelyne vapor barrier over the top of the concrete prior to installing the flooring, and no other subfloor or underlayment is necessary. For more Information on warranty or installation, we recommend reviewing the Warranty and Installation Guidelines (found in each carton or on the product page of Lowe's website). Hope this helps answer your questions. Thanks again.