You might want to check these out.
http://www.mwave.com/mwave/viewspec.hmx?scriteria=NB-BA20408
This one has about a 1.5 hour battery life, big heavy, but its powerful, A64, ati 9700 128,, and starts at $1250.
Mitac 8050 , sold as the voodoo M something.
http://rjtech.com/8050.htm
ok its smaller lighter, alot lighter, abit less powerful with a P-M dothan, but has the ati 9700. Battery life is in the 3 hour range.
starts at $1319, you could get a pretty nice one for 1500.
The Asus M6NE or M6bNE depending on if you want a 15.1" sxga screen or a Wxga screen.
http://1toppc.com/Merchant2/merchant.mv?Screen=PROD&Product_Code=M6BNe&Category_Code=Notebook
I bought this one, so I'm biased. P-M dothan Ati 9700 64Mb, batterylife in the 4.5 hour range, this was the deciding factor for me. optional 2nd optical drive battery, which kicks it up to 8.5 hours. I bought from there too, they were good, no problems.
your looking around 1458, with a 1.7 dothan, 40Gb harddrive, Wireless, 512ram, and CD-rw/Dvd.
The asus, is a little more rugged than the others. Now I don't know about doom 3 but these are powerful laptops, for a good price.
I hope this gives you some ideas.