I was looking at Rock's laptops and bless their honesty, they even admit the battery life is 1 out of 5 stars (for the SL8 model at least).
If your graphics is not overly intense, you can go with a Sony laptop. I use a Sony for personal use which I purchased this past December. At the time, it was the top model they had (VGN-FZ290)
Specs:
Core 2 Duo 2.6GHz
4GB Memory (3rd party vendor)
7200kRPM Disk (3rd party vendor / Hitachi)
Nvidia 8400M GT with 256MB Dedicated / up to 1GB Shared
Blu-Ray Drive (amazing quality rest assured)
At the time it was $2,300 estimate for the total price. If you compare with Alienware which has advanced features currently, pricewise is still a major difference.
You'll need to do your homework and find your right balance.
The Sony is extremely slim for its specs, sleek and the battery lasts about 5-6 hours in general use (wifi, typical software as Office, video streaming, etc).