What I'm wary about is the choice of Windows XP - the computer will outlast the operating system given that MS is discontinuing quite a lot of software for that
EOL'd OS. You're stuck with IE8 (which is a hazard) and Office 2010.
If I were building it I'd drop to an AMD APU build to save up for Windows 7/8 or run the computer with Ubuntu instead of running Windows XP with all its unfixed exploits.
As for your CPU/IGP question, I don't notice the difference between my laptop's mobile Core i5 and my desktop's i5 2500k with web browsing and MS Office. Really those basic tasks + any modern processor will actually get you hard drive bottlenecked before being CPU bound. Someone who does more stuff off an Intel IGP can chime in, but I have no problems with YouTube videos and similar on my laptop running Intel 3000 graphics.