Internet Connection Speed Problems?

[AlphaAlfalfa]

I don't know why my internet speed is so slow. I always experience lag when I play online with my PS3 and PC.

I've already made sure my PC is good, from removing programs to getting better hardward.
I've already called my ISP and confirmed I have good internet (supposedly I already have the best plan).

I'm thinking it's either my modem or lack of a router, but from what I've read online, those don't affect your connection to the internet.

Regardless, my current modem is this: http://www.amazon.com/2Wire-3800hgv-b-2w...B0042IEZSO
and honestly I think it sucks, but I'm still not sure what the problem is.

All my connections in the house are wireless. I know using an ethernet cable is vastly superior, but I can't since my dad won't let me snake the cable through the house (just don't bring up ethernet cables).