I just got a inspiron xps with 128mb 9700. You can get a 9800, but is it worth the extra money to upgrade. Is there is big diff. in fps. in most of the recent games? It already has a 3.4ghz with 1gb ram?
Mobility 9700 has 4 rendering pipelines compare to the 8 on the desktop 9700. Performance is much closer to an overclock 9600 pro desktop version. Money/preformance wise, i dont think it worth upgrading to a 9800. Just play your games at a slightly lower resolution.
The difference is like going from a desktop 9600 (as RQLe said) to a desktop 9800/XT. The Mobile 9800 is actually based on a slower running X800 core. It would only make a real difference in a few of the very latest games like Doom 3 and future games.
It's $399 to order from Dell, but if you cancel the installation and do it yourself, you should be able to get $100 off that price, making it around $300 (cheaper if you have a coupon).