Debating on Desktop Replacement or Desktop + Laptop

I'm going off to college within the next five months, studying Computer Science. I'm torn between building a system, around $1500.00 - $2000.00, and purchasing a $1000.00 laptop -OR- purchasing a $2500.00 laptop which would offer the capabilities of mobility as well as providing the ability to utilize an external monitor, keyboard, mouse, HDD, et cetera.

I'm not willing to spend much more than $3500.00 for either setup (and preferably less for the desktop replacement route). Which option would be the most cost efficient for the next four to eight years of student life? My primary uses will be medium-level gaming, CS4, programming, and MSOffice. Finally, if you would be willing please provide examples of laptops that would be suitable for the following needs...

• 120 Gigabyte HDD Minimum
• HDMI-out
• Dual-layer DVD Burner Blu-Ray preferred
• 12-17-inch display
• 2 Gigabytes of RAM

My original intentions was a gaming rig with a netbook. However, from the few netbooks I've gotten my hands on, I'm not too impressed. The terribly small keyboard is the biggest turn off, not to mention a tiny-ass screen.

I assume you're referring to the U100? How is the keyboard?

I'm also thinking about buying a high-end laptop. I went to the Sony store today and saw a VGN-AW290.

Intel Core™ 2 Duo Processor P8600 (2.40GHz)
Microsoft Windows Vista Home Premium 64-bit
2GB DDR2-SDRAM (DDR2-800, 2GBx1)
320GB SATA Hard Disk Drive [7200 rpm]
CD/DVD Burning Drive
XBRITE-FullHD™ (1920x1080) with Adobe® RGB color management
TV Tuner
WLAN (802.11a/b/g/n) with integrated Bluetooth technology
Standard Battery

OPTIONS
faster CPU
up to 8 GB RAM
up to 1TB hard drive
Blu-ray Disc™ Read and Write Drive

http://www.sonystyle.com/webapp/wc [...] 1665736378

I don't work for SONY, I just happen to notice that particular laptop. Also on my list:

HP HDX 18

http://www.pcworld.com/reviews/pro [...] dx_18.html