What is the best brand of SSD to use with my desktop?
Good budget models are Inland, Silicon power, PNY, and Adata. All of them work well as a fast boot drive.
For a battler quality and longer warranty use Crucial MX or Samsung EVO series. They’re essentially the same, but the Crucial tends to be less expensive.
Upgrading refurbished Dell OptiPlex with any of these brands is the best way to make your system more responsive.