Beginner's question - Laptop CPU Comparison

I tried searching the forums, but didn't find the exact answer I was searching for.

The Situation: I've been researching on buying a new laptop which is mostly for Business use, and some part-time gaming as well. In the last few months, I see a lot of Centrino 2 laptops springing up, and I was specifically interested in the new Sony Vaio SR series - due out in August.

The problem: Most of the sites I see are coding their laptop CPUs as P8XXX or T9XXX. With little to no additional information given on the difference between the two. I know that the 'T' Series laptop CPUs have been around for a while (Dell XPS M15XX / M17XX, Vaio Z series, Asus - can't remember model sorry ), and I *think* the P series laptop series are the centrino 2.

The question: Is the P series - even at a lower clock speed - 2.2 - 2.4 GHz actually faster than the T series 2.5 - 2.8 GHz?

Any help to a confused buyer would be genuinely appreciated!

Sorry - it wont let me edit the post

I figured this out now. Apparently the FSB speed was the main difference and as it turns out, the T9600 is in fact much faster than the P8400 / 8600.

A second question however - The graphics card offered in the system is the ATI HD 3400 series with 128 mb ram. How easy (or difficult) is it to actually replace the graphics card in a (Vaio) laptop? Is there even the remotest possibility that I could plug in a off-the-market 9800M GTX?