R7800 Speed Issue

Thanks for the suggestions.  Access control, traffic monitoring, qos and parental controls are all disabled.  I rolled back the firmware version to 1.0.2.68, then did a restore configuration, no change.  Then did a wipe and a complete manual rebuild, no change (actually that's not true, things got worse).  So wiped and restored from my configuration save.  Got speed back up to mid-200s but still no where near what I see at the modem (~500down/30up).  I'm starting to fear this just isn't going to work.  If not then I'll be looking for new router because I'm getting tired of fighting this battle.  Shame too, I always liked this router.

Absoflutely open to other suggestions.  To date I've:

1) physically moved the router right next to the modem and used different Cat6e cables to make sure it's not a cabling issue (no change)

2) disconnected all devices except my desktop computer (turned off wireless also) so that my computer was the only one using the connection (no change)

3) did a soft reset using the OS on the router, then restored the configuration from a save (no change)

4) did a hard reset with the reset button on the back of the router, then restored the configuration (no change)

5) physically moved the router back to its usual location and plugged everything back in (network cables and usb drive) (no change)

6) did a soft reset then rebuilt the configuration manually from scratch (things got much worse)

7) restored the configuration from a save when #6 made things worse (that's puzzling) (back to original ~200s)

8) upgraded firmware to 1.0.2.74, rebooted then restored configuration from save (finally, some improvement)

With the last change (#8) I'm now seeing speeds in the mid to upper 300s (and an occasional 400+).  For now I'm gonna stop.  Not going to call it solved, so if anyone else has any ideas, I'm certainly open to suggestions.

Thanks all, really appreciate the suggestions!!