Took me a while to understand your situation, and I'll summarize it here.
You had a Netgear G54 wireless router before, you connect your main PC to this using an Ethernet cable (not hard-wired, hard-wires could means soldered into the device, unplug-able.), you can achieve download speed (through VPN) up to 1.4Mbps.
You currently on a new wireless router DLink DIR-615 (N150, not N300) and the overall speed dropped by 80% (left 20% or dropped to 80%? Please clarify), the new laptop is also connected to the wireless router at the same time (or was it not??) doing normal surfing, no connected to any VPN.
Now if my understanding is right about your situation, your overall speed left 80% which is around 1.0Mbps peak speed? And at the same time the laptop connected to the wireless router is doing some web surfing.
Questions:
1. What's your ISP, and subscribed package? (i.e. StreamyX, 4Mbps Combo)
2. Do you have anything connected to your wireless router (Netgear G54) before you switch to the new one? (cable or wireless)
3. How did you setup your new wireless router? Is it WiFi protection up and running? (WEP, WPA2, etc.)
4. Have you ran speed test to ensure your connection is up to the expectation? (please post your result for both router)
5. Have you tried not to connect the laptop and download?
6. Is the condition of the download similar or same as before you switch to the new wireless router? (using BT?)