[zx10guy]

Not necessarily. I've had many discussions about this on other forums where there's a misconception about how a particular network device performs. Just because a particular network device has a particular physical port such as 100 Mbps or even 1 GigE, doesn't mean that device is going to be able to perform at those speeds.

For firewalls, there's a ton of processing happening in the background many people don't even think about. There's a routing component; although for a SOHO router there's not much to the routing table. But nonetheless, there's some processing involved. Then there's the NAT function or more specifically the NAT overload which the router/firewall has to keep track of. And then finally, there's the actual firewall function. For SOHO routers, the firewall function is only stateful packet inspection. While SPI is not as intensive in regards to processing as deep packet inspection found in next gen firewalls, it does consume processing power.

An example of this is the firewall I use on my home network. It's a Sonicwall TZ400W. This firewall has 1GigE ports on it. The manufacturer specs for the firewall for SPI is 1.3 Gbps. But when DPI is turned on, the performance drops to 300 Mbps. So the point is, you won't know what the actual performance of a given firewall/router is unless the manufacturer provides those specs or there is a review with actual load testing.

And on the topic of wireless interference from neighboring wireless networks, yes, this will impact wireless performance. Typically looking for a different non-overlapping channel will fix this. If you're operating on the 2.4 GHz frequency, moving to 5 GHz will also help as 5 GHz has more non overlapping channels available. But your wireless devices have to be able to support 5 GHz before this is going to be a solution.