What I did before I got myself a surround sound system was to simply go to my local Radio Shack and buy a cable that takes composite stereo audio and converts it to a stereo 3.5mm headphone jack.
Plug the converted head phone jack into the Line-In jack on your sound card, make sure that the volume is turned up on that jack and it's not muted, and you're good to go. It's not the best solution, but it works.
Also, there's no point in an Composite to S-Video adapter, just buy an S-Video cable for the PS2. You can get that, and the other cable at Monoprice for pretty cheap. The problem with Monoprice is you have to buy a fair bit of stuff to make the shipping worth it. But I've bought probably over $100 worth of cables from them over the past couple of months, and have been quite satisfied, and even impressed, with their quality. They're probably every bit as good as premium quality cables like those Monster sells, at a fraction of the cost. The VGA cable I picked up for my 360 has been excellent. Huge improvement over the composite video cable I was stuck using for a couple of days.
Also, TV tuners tend to have about a 2 second buffering delay, so they don't work well for consoles. Maybe if you're playing a JRPG, where the combat is turn based it would be workable, but I think it would get real old real fast having such a big delay between the time you pressed the button and saw the results on the screen. In almost any other type of game, it just would be completely unacceptable.
I own a Gateway 24 inch monitor (FHD2400) and use it for my computer. However, I am interested in hooking up my PS2 to it. I could get the video working by using a converter to convert it from composite to S-Video, but my speakers are connected to my computer, so I don't know how to get the sound to work. Would it be easier to just install a TV tuner and use it through that?
Thanks for your help.
And btw, I'm a new user and apologize if this is in the wrong forum or I made some newb mistake.