I hope its ok to ask a 1/2 Apple, 1/2 PC question

This is an iTunes question..

I just bought a new computer (PC). I installed my old drive as a second drive on the new computer.

I installed iTunes and pointed it to my old hard drive's music folder. When all the music was loaded I noticed that it said 4,057 songs. But my iPod says almost 6,000 songs.

To complicate things, I have since bought some new music that I added to the new library. So, I can't just delete the library on the new computer and rip iPod.

Is there a software that would allow me to do a side by side comparison of iTunes library and iPod library so that I only transfer iPod songs that are not already on new computer?

I have looked into different programs- Senuti, Cucusoft etc..
but I can't tell if these programs allow you to do the side by side comparison. I don't want to end up with duplicates if the software transfers my entire iPod. And I need to see the libraries side by side to see what I am missing.

Also, if I could transfer playlists, that would be great.

And finally, I heard that sometimes music gets snippy/choppy after it is transferred. Are there programs that are better at maintaining the music quality?