I just updated Firefox and, so far, there isn't any more lag on my PC.
I'll test my gaming hopefully tonight to see if I'm still having issues on that end.
You know what's funny though but kind of unrelated. I was chatting with this employee at Best Buy earlier who I see all the time and is super cool. He seems like a pretty knowledgable guy and when I started talking about how people were telling me that I should set up a static IP for my console and open/forward ports in my router he just laughed. He basically said he thinks all that stuff is a pain in the dick too. He said the same thing happened to him when when he tried doing that with his PS3. He couldn't get online with his 360 or his laptop.
If he couldn't figure that out, he's nowhere near as knowledgeable as you think he is. Not to sound like a snob but if the guy is working in a tech role at BestBuy, that's the equivalent of an aspiring chef being a dishwasher at Swiss Chalet or to be more in common with your line of work...an aspiring police officer being a rent a cop at an old age home. Just so you have some perspective on your typical department store tech guy's skill level....anyways, gonna throw some random ideas at you.
So just for shits and giggles, disconnect all your systems from the network (at the physical level) and then see if your PS3 games are laggy. Basic process of elimination troubleshooting, if the PS3 is the absolute only item connected in your home network and you still experience issue then it's either something happening at the router level, or with your ISP. If there no longer is an issue, then I'd assume it's something inside your network causing this problem. You could use
www.speedtest.net to verify you're getting the correct bandwidth to your home. Run this from a PC when you are experiencing issue just to verify the ISP is providing you the expected speeds.
Possible that someone has turned your PC into a slave in a botnet without you realizing it?
I don't think you're tech savvy enough, but you could attempt to take a look at...
http://download.cnet.com/Bandwidth-Monitor-Pro/3000-2085_4-10217766.html
...and take a look at your network traffic to see if anything is going on there.
If you believe that someone may have accessed your network I would advise you change your router admin password and WLAN key, I mean it should be done every so often anyways but I realize most people aren't comfortable enough to change things once they are working...so...yeah.
Looking at your router config just checking to be sure no unknowns are connected to it should be done as well. You should be able to find a list of connected devices to rule out any local/nearby unwanted access.
Another simple point but always needs to be asked...downloading. Torrents, P2P, windows update, application updates....on any system? You're sure?
When you follow any advice I suggest,
don't assume and always be sure. Just keep that in mind when you check each thing out.
If I can think of anything else to throw at you I'll post again later.