R7800 Speed Issue

All:

Thanks very much for the feedback and suggestions.  I finally got the problem resolved.  To summarize here's a short list of everything I did:

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)

9) reviewed and tweaked all settings based on the feedback/suggestions from this forum (again, THANK YOU!)

So the problem finally cleared up.  The real solution?  I had the cable R6 coax from the pole to the house replaced.  It turned out the squirrels had been chewing on the line and it finally failed necessitating having the cable company come out and replace the cable and check everything over.  I'm now consistently seeing speeds in the 450+down and 30+up ranges

Thanks all, really appreciate the suggestions!!