I'm experiencing quite low speeds through my E2000 using 802.11n over 5 GHz (about 36/19 Mbps), but I reach the full 200/20 using a wired connection. If I connect to another router downstairs (also 5 GHz), I get about 120/16 Mbps. My router is about 1.5 meter away from me, so the signal strength is nearly at maximum as well; I get about -41 dBm with an SNR of 50 dBm. On the entire 5 GHz band are 3 networks, so all in all I guess the signal itself is fine.
I've also "underclocked" the CPU back to 300 MHz.
I first flashed the router with the wiki recommended build 14929 (I used the std_usb_ftp version). However, I noticed that my wired speeds were not optimal (barely 60 Mbit), so I kept upgrading my router until I found a build that would reach full wired speed. Eventually I ended up with dd-wrt.v24-18767_NEWD-2_K2.6_mini-e2000. I'm using mini because I need JFFS support and that won't work with the big or mega builds.
I found a bunch of tips about tweaking the wireless settings on the wiki and through Google. This is my current and (for now) most stable configuration:
1) Would the channel really matter? Not that I'm not willing to try, just wondering what changing to a channel around 52 would do.
2) I also tried the build in the router database (21061 mini) but SSH was broken on that. The wireless performance hasn't changed much over all the builds I've tried.
I'm aware that its wireless is mediocre at best, but I feel like I should be able to get at least somewhere between 60 and 100 Mbit down. Especially considering it's running on 5 GHz only.
So I changed the channel to 36 and it seems to have improved stability a bit, but not the speed.
Also worth noting (I think) is that NAT/routing is off and that that's done by another device. I know the E2000 has limited WAN throughput in case of NAT (~120 Mbps down on cable, 200 without it doing NAT).
The E2000 still connects to the outside using the WAN (now switched) port, but I separated the two networks with VLANs and ebtables. Everything is working as it should, with the exception of the low 802.11n throughput.