Packet Loss, High Ping/Latency for PC's when gaming

Hello, about 4 weeks ago we started experiencing Packet Loss and High Pings while playing games. This affects our 2 PC's and our PlayStation 3 (Since we use them for gaming). We have contacted our ISP several times regarding the issue but each representative we have talked to has had different ideas of what the problem is. They replaced the modem twice which did nothing, so I then purchased 2 new Router's (DIR 601 N150 & DIR 835 N750+). Neither of them solved the issue. my ISP also says it isn't the Internet Cable that is causing the issue. My Download Speeds and Upload Speeds are right where they should be but the ping and the packet loss is the problem. I also contacted DLINK (Router Manufacturer) to see if they had any ideas and all we did was upgrade the firmware version and change the Wireless channels which also did nothing. I have plugged this PC into the modem with an Ethernet Cord and played games and all the issues were gone which leads me to believe that Modem and the ISP aren't the issue.

Things I've Tried:
-Resetting the Modem
-Testing each Wireless Channel on my Router
-Enabling and Disabling 802.11n and 802.11g on the router
-Changing the QoS settings
-Installing Software such as Gamebooster and Advanced System Care
-Disabling all Antivirus programs and Firewalls on the PC's
-Using a friends Modem instead of the Cogeco one (no help)
-Turning all game settings to low
-Updating driver software for the Network Adapter (which is just the Ethernet Cord)


Notes:
-If we only have ONE gaming platform on at a time there is a lower ping but still higher than usual
-The PC i'm using now is connected to the router with an Ethernet Cable, everything else is wireless
-We have 2 PC's, 1 IPAD, 1 IPOD, 1 Laptop, and 1 PS3 which are all usually on at the same time (6 devices)
-These problems started around the time we got our new PC, but even when it isn't connected to the Internet we still have the High Ping and Packet Loss on the other PC and PS3
-Before this all started we were able to have multiple devices playing games and streaming videos and downloading stuff without any problems
-My ISP is Cogeco Cable
-My current Router is the DIR 835
-My current Modem is the TM602G/115
-The games start off with high ping, then drop quickly to a very low ping, and then shoots right back up to a high ping again and it never goes down.
-Even after exiting the games we still have High Pings while web browsing
-Resetting Router helps until we try to play another game
-When I plug a PC directly into the Modem that PC won't experience the High Ping in games which leads me to believe it is a Router issue.

I will include my System Specs even though this PC isn't the only one having the issues.

OS: Windows 7 Home Premium 64-Bit
System Manufacturer: Acer
System Model" Aspire M5802
Processor: Intel Core 2 Quad CPU
RAM: 8GB
Graphics Card: AMD Radeon HD 7800 Series (7850 to be exact)

High ping times to where, exactly? Other PCs on the network? The router? The modem? Google? The game servers?

A shot-in-the-dark guess is that your wireless is overloaded with the high traffic of the game. Only one device can transmit at a time with wireless, so if you introduce to much competition, everything suffers. Adding a single computer may break it for everyone.