Quality of film gets reduced when exporting it

I edited a film on FCP7 that I shot on a DSLR. The film will go on Youtube, so I watched a tutorial on how to export in fcp7 for youtube, and followed what it told me to do. Here are all of my export settings:

Compression Type: H.264

Frame Rate: 30fps

Key Frames: All

Data Rate: Restrict to 8000 kbits/sec

Optimized for download

Dimensions: HD 1920 x 1080 16:9

"Prepare for internet streaming" is checked.

Here's the problem, when I watch the finished film after I've exported it, the quality seems to have reduced, and so has the color a bit (this is compared to the original footage that I shot). I do not know what I'm doing wrong at all, and I hope someone could help me fix this problem.

Here's a screenshot from the original footage:

[IMG]http://i61.tinypic.com/6jpow8.png[/IMG]

And here's a screenshot from the exported footage:

[IMG]http://i57.tinypic.com/2zr2wjt.png[/IMG]

Another example:

Before: [IMG]http://i60.tinypic.com/fva4q9.png[/IMG]

After: [IMG]http://i61.tinypic.com/2hz7pq9.png[/IMG]

Thank you in advance.