youtube laggy with sound delay

[spiritusinvacuo]

Greetings Mint Community, total Linux newbie here!

I'm trying to switch to Mint after good 20 years of Windows experience, and I really like it, but I'm having issues with playing Youtube videos (especially when I switch to HD quality).
After installation, videos were horribly laggy and sound was somehow delayed by video for 0.5 second which is not terrible I guess, but still annoying.
I've found here that problems can be fixed by installing Adobe flash and proprietary AMD drivers, which I did, and although quality of videos has improved drastically, it still lacks the fluidity that I get on Windows 7, and sound is still delayed.
Can I do anything else to further improve smothness of video playback (especially flash I guess) and get rid of that sound delay?
Playing 1080p rips was also lagfest, but AMD drivers seem to have fixed that problem.

I really like the Mint and I'm hoping it's going to be the one that will make me switch full time from Windows, but this kind of issues are really frustrating.

My computer configuration is:
Intel E2200
4gb DDR2
EP35-DS4 gigabyte motherboard
ATI 4850

Thanks!