DIR-655_A1_fw_1-11EUb02
This is by far the best firmware that i've found... I've had it for 4 years and its yet to crash or any other problem. It's incredibly stable.
The wireless works amazingly well compared to other firmwares. I get 50% signal 3 solid walled rooms away. The position of the router is very importante, aim the antennas where your going to be using the wireless. It seems as though it's best if the router is sitting with its antenna facing upwards into the sky, change its position until you get the signal just right.
As for wired connection, it works incredibly well too. No problems after 4 years. Not one drop.
The problem with this firmware is that it's one of the early ones and thus doesn't have some of the later features, such as shareport etc. But for the main things that you want a router for i.e. wireless, wired, Multicast Streams etc... It works really well especially for the main things that you would use it for the most.
Imagine that 4 years without 1 problem....
Highly recommended!
If you can't find the firmware, it's here: http://www.dlink.com/uk/en/home-solutions/support/product/dir-655-wireless-n-gigabit-router?revision=uk_reva2