Bad advise for current tools: you need to settle on the battery system, since batteries are expensive. I.e. once you start replacing, it’s going to be a single brand, but the trick that you can get great set of batteries and tools as a bundle at large discount. DeWalt in particular, and others, often have great bundles and sales. So if you more or less know what you need, you can get good quality tools at discount by choosing correct bundle, replacing them one by one would be way more expensive.