Awful WiFi speeds, something wrong with this adapter? -- Inspiron 3521, Dell Wireless 1704

EDIT: The problem has been resolved! Please see the bottom of the post for my device settings.

Hello, everybody.

I've been struggling with this problem since I got this computer. There are 4 other computers in the house all averaging around 17Mbps, while my new Inspiron is getting below 6.

I've tried so many different things but I'm at my wits end here. I would prefer not to have to send my new laptop back for repairs/replacement, but it's looking more and more like that is the likely outcome.

I'm currently running Windows 8.1, though the speeds were still horrendous before this upgrade.

I check my speeds via speedtest.net


Here is a list of what I've tried (that I can remember):

- Uninstalled the wireless adapter from my device manager. It actually ended up coming back with the name Broadcom 802.11n. I was concerned about it not having the B and G so I did a system restore to get it back to how it was.

- I changed the following values under the Advanced tab in the adapter's properties:
  Antenna Diversity: Aux
  Minimum Power Consumption: Disabled

- I installed both the regular and the Windows Update drivers from the driver's page on the Dell website for my computer.

- I installed the unofficial drivers for the Dell Wireless 1704 from http://dellwindowsreinstallationguide.com/driver-sets/dell-wireless-cards/


Literally none of this has made an impact. I sit roughly 26 feet away from the router with this laptop, but bringing it right next to the router doesn't seem to make a difference.

Earlier this morning it was getting expected speeds, but after a while it diminished to it's usual 6Mbps and below.

Any help is extremely appreciated.
Cheers.

EDIT: Here are the settings that resolved the problem for me, thanks to Jasmeet at Dell's technical support!

Power Management:
- Allow the computer to turn off this device to save power: Unchecked

Advanced:
- 20/40 Coexistence: Auto
- 40MHz Intolerant: Disabled
- 802.11h+d: Strict 11
- 802.11n Preamble: Auto
- Antenna Diversity: Main
- AP Compatibility: Higher Performance
- Bandwidth Capability: 11b/g:20/40MHz
- Bluetooth Collaboration: Disable
- BSS Mode: 802.11n Mode
- BT-AMP: Enabled
- Fragmentation Threshold: 2300
- IBSS 54g(tm) Protection Mode: Auto
- IBSS Mode: 802.11b/g/n Auto
- Locally Administered MAC Address: Not Present
- Minimum Power Consumption: Disabled
- PLCP Header: Long
- Power Output: 100%
- Priority & VLAN: Priority & VLAN Disabled
- Rate (802.11b/g): Best Rate
- Roam Tendency: Aggressive
- Roaming Decision: Optimize Distance
- RTS Threshold: 2300
- Short GI: Auto
- WMM: Auto
- WZC IBSS Channel Number: 11(20MHz)
- XPress (TM) Technology: Disabled