Can my laptop be too weak for internet browsing?

[Attila]

I have a 4+ yrs old Asus laptop - Celeron T3100 processor, Intel GMA4500M video, 2+2GB (upgraded) DDR2 memory, 128GB SSD (upgraded), Windows 7 Home Premium, Comodo Personal Firewall, Microsoft Security Essentials.

I recently noticed that complex / multimedia-rich websites (eg YouTube, Pinterest, Tumblr, Facebook, One Green Planet etc) work slower than before, especially if I have them open on more than one or two tabs. Sometimes the whole browser temporarily becomes unresponsive for 1-5 seconds. Videos / Flash ads often not play very smoothly.

The problem persists in Firefox, Opera, IE, Chrome. I restored the original drive image (Windows), let Windows to install updates, then I installed the browsers and software. No joy, those websites are still not faster.

There is no problem with those websites on my desktop PC (AMD proc / Geforce video gaming PC) or my wife's PC (Intel I3 proc / Radeon video gaming PC). I also have and Asus Eee netbook, that struggles with those sites even a lot-lot worse than my laptop.

Also noticed, that my laptop won't play full HD movies smooth (and my netbook won't even play standard definition movies smooth) - so I guess their video chipsets not powerful enough.

Based on all the above I got a gut feeling that maybe by now, as websites have more and more images/videos/Flash/interactive content, my laptop's (and especially my netbook's) processor, or rather video, is not enough for these websites anymore? Do I need a better laptop?
... and it is not only just video! A great example can be this site: http://www.sky.fm/newage
My CPU usage is moving between 0% and 8% (idle). Then I load the above site into a browser. As soon as the music starts playing the CPU usage jumps to quite high:
Internet Explorer: CPU usage in the 20% - 30% region
Opera: CPU usage in the 30% - 45% region
Firefox: CPU usage in the 55% - 75% region
Google Chrome: CPU usage in the 80% - 95% region
:-(