I recommend OpenWRT. But first, make sure you know what you are doing. And yes, it will most probably void your warranty if it bricks with the OpenWRT firmware on there. Replacing back the TP-Link stock firmware (yes it's possible), and resetting the flash counter, if any (I don't think there is one), to zero, should return the router factory new (and warranty should be claimable).
OpenWRT has become easier and easier to flash. It has comprehensive documentation, and a HUGE number of packages. DD-WRT is based on OpenWRT. From
http://en.wikipedia.org/wiki/DD-WRT: "The Linux kernel part is based on the OpenWrt kernel, which started as Linksys-based firmware but was later changed to its own build framework. All of the firmware is based on Linux, as are OpenWrt and Alchemy."
Of course, we need to know what TP-Link router it is.