I can't see so good

Happenstance

I've become addicted to watching music videos on-line, like on YouTube through RealPlayer and QuickTime and Windows-Something but the images are too small and when I pick the full-screen size the image is either too blurry or too pixelated, ya know? And a lot of times, the image is too dark.
I have an old-ish monitor that's not very big, the screen is 13x9 or 16" diagonal and it's perfectly fine for all other purposes. But would getting a new monitor fix video viewing for me? Or does that not really matter?
It just seems like people talk about seeing things in a video that I just can't make out. So is it my monitor or do videos pretty much suck on home computers no matter what?
It's only a minor annoyance with Pearl Jam but a MAJOR problem with NIN videos (which are dark by nature of course).
Advice, please and thank you