Please Please Please recommend me a Linux Distribution.

Here are the specs for my desktop computer. I have a PCI Wifi card inside that I put in. It uses a Atheros chipset.

http://www.dealigg.com/story-HP-Pavilion-p6350z-series+

I'm looking for a distribution that has KDE as an option or the default. Since its the closest desktop environment that resembles Windows. I do that so my wife won't get annoyed and worst case scenario tells me to put Windows back on the machine. Although I would love to use Xfce.

This is what I am looking for in a Linux distribution and in no particular order:

1. Speed. I have a few Windows apps that don't run perfectly in Wine and I will be using Virtualbox. I just hope Virtualbox the performance is as close to native Windows. I will probably just use Windows XP in Virtualbox.
2. Has a good repository of programs that I can pick from. I just don't want to only pick from 100 programs only available to me.
3. When new Linux software gets released I don't want to wait six months or a year to download it. I would like it to be available within three months.
4. Ease of use. More for the wife than myself. I would not mind getting my hands dirty and typing in commands. I love Linux and don't mind learning. This will help putting it on my resume.
5. KDE. What I mentioned above.
6. Security. Looking for a distribution that does care about security for its end users.
7. Nice to look at. More of an option though.
8. Stable. I know Linux has legendary stability but you never know with some other Linux distributions.

I hope I can get help with this. Thank you.