Being DSL, you're limited to what is compatible with your ISP. 5mbps is not a great package, and whatever you do, it is going to be slow, especially if your brother / mom starts watching movies, and there's nothing you can do, even with unlimited budget.
What you might do - put existing router in bridge mode (or get just a DSL modem), and start looking for router with Ethernet WAN interface (most so-called "cable" routers) that has the options you need, or can be flashed with custom firmware.