x2 trying to flash it with DDWRT or Tomato. Each relative website will list compatibility. Worth a shot since all else has failed.
If you need to replace it, I bought a TP-Link Archer C8 a few months back and honestly, it's been the best damn router I've ever owned. I was dodgy on the TP-Link brand until I read a lot of good reviews about this router in particular, so between the reviews, the salesperson confirming good experiences, and the 2 year warranty, I bought it.
It's GREAT. I was a Cisco/Linksys guy for years but their stuff has went downhill and my last Cisco router lasted barely more than a year, just out or warranty. The one before, barely 2. They never performed great....their firmware always sucked so I was always flashing with DD or Tomato anyways, but after going through 3 of them in 5 years, enough.
The C8 however has been stellar. Thoroughput is excellent, even with a 100 meg internet connection, I can saturate the wireless internet (and get a solid 100 megs through it virtually anywhere in the house over both 2.4 and 5.0) and still get 500-900 megs between computers or other devices in our house (intranet)
at the same time. Unheard of with my previous hardware. And it's solid through it all, never crashes...and the firmware is surprisingly versatile - I've had no need to try to flash DD or Tomato, honestly.
And it's on sale right now on top of it all at Canada Computers, having just looked.
http://www.canadacomputers.com/product_info.php?cPath=27_1046_1047&item_id=079596