I would say go DELL, nothing but satisfaction from my side.
I have the Inspiron 9100 (2 years old already) and have played all the latest games, up till Doom3 and Fear Demo (128MB ATI) on it, without any problems. It performs the pants of most systems. I even played host server for LAN parties!!

Support has also been great. I love their products!!

I have been looking around for a new one for some time and will definitely go Dell again, if not even more niche, like Alienware.
Dell's Precision (they call these 'workstations', built for performance and mobility) notebook range is excellent, and is geared towards your requirements. The M90 is the latest and greatest. An absolute MAX spec will cost you about 30K, but I think you can change this a bit to get it closer to your price levels.
You might try the Latitude range (D620, D820) as well, it is geared to business, but it might cater for you as well. These systems have long production cycles.
They just brought out the new Inspiron 9400 (latest technology, not long production cycle) as well, and this will also do what you want it to. The options are endless. Happy shopping!!
If you are limited to 20K for the notebook, then you will have to make some compromises. It is not very much for a high-end notebook.
I spit *spit* on HP....