You are paying a huge premium right now for any notebook that has 256mb dedicated video RAM in a notebook. In fact, there are only a handful of Pentium M notebooks that have even the ATI 9700 video card with 128mb video RAM (and the Athlon 64 notebooks out have 64mb dedicated video RAM max).
Also, Windows Longhorn in late 2006 or 2007 is going 64bit so you don't want to pay more than $1500 now (or $2000 at most) as you notebook will be obsolete then 64bit hits in earnest (Linux versions are 64bit now).
The Athlon 64bit notebooks will run 64bit but they only go to 64mb dedicated video now as I said.
Unless you have money to burn I would save your money and at least wait for the 2 cpu 64bit chips to come out later (it could be next year but no timetable) and wait for the 256mb video cards in notebooks to become mainstream.
I'm sure the 256mb video card notebooks you are looking at must be close to over $2500 and that is too much to pay for a notebook that will be obsolete by 2 to 3 years maximum from this date.
You can easily get an affordable desktop and pop in the top video card for $500 or less and hold onto your cash until the notebook technology catches up.
128mb dedicated video notebooks will play many games very well but if you are focused on Half Life 2 it may be at reduced settings. The HPzd7000 is a highly rated notebook at zd7000forums.com (see cnet reviews) with a 17" LCD but of course battery life is under 2 hours. Dell has a Pentium M model with the Hitachi 7200 rpm hard drive and ATI 9700 with 128mb dedicated video available and a 17" LCD -- and the Dell 8600 (Centrino) also has the 7200 rpm hard drive and 128mb dedicated video with a 15.4" widescreen.
Im looking for a notebook I can use to play the latest games (theres a lot of these posts coming up). The only notebook that offers a 256mb gfx card are the dell xps and I believe one of the pacer(pager i forget) notebooks. Mainly focused on the game HL2, its making buying a notebook hard because that game already makes some of the new notebooks look obsolete. Rumor that theres new notebooks coming with atis and nvidias new 256 cards and have the ability to change gfx cards around christmas. Im not sure if this is true but Im not buying a XPS or that pacer notebook, nor the zd7000 or toshiba sattelites since they only have 128's in them. Main Question is: Should I wait until Christmas-Newyear to buy a notebook?