TL-WR841N router upgrade and replacement

I'm currently using a ARRIS SB6141 along side a TL-WR841N wireless router for my time waer home inteet setup. It working well when I'm right next to it with my laptop. However, when I'm at the other end of my apartment (only around 30 feet away) the speed is terrible. The signal still appears to be strong on my laptop but the speed goes to less than 1/4 of what I am getting close by.

What would you recommend I try as an upgrade to fix my distance issue? I also have regular issues with the setup dropping coection. I hope to also fix this with the hardware upgrade.