Out of interest what operating system are you using? The issue you have described can often be down to windows settings for networked devices. IF IT IS Windows Have you tried running TCP Optimizer?
http://www.speedguide.net/downloads.php
NOTE:
make a note of ALL settings it displays upon loading, also save the current config when you have loaded the app. (File > Backup current settings).
Then select your wireless network adapter in the Network adpater selection drop down box, move the speed slider up to what your connection speed runs at or as near as you can get it (around 74Mb for you) click "Optimal at the bottom, click apply changes.
Shutdown PC entirely (complete power off)
Power off and power the router back on (wait 30 seconds or if you feel really up to testing reset the router entirely)
Power router back on
Power computer back up
Now run speed tests, does that help? If not or it is worse reload TCP optimizer and load back the backed up settings... Then go through the above powering up and down bit again to go back to normal.
If you are running a linux variety you need to alter RWIN via command line. Ill go into that more if needed.
If its a MAC i have no idea.