Help me decide on a new computer

I sold my three month-old laptop last week, I just got tired of Vista and the company I work for gave me a brand new mb pro so no need to have two lappies. Now, I never want to touch Vista again… ever. I’m serious. Here are my choices: a brand new 20″ , 2Ghz, 2Gb ram, 250gb iMac OR I could screw the iMac and build myself a monster rig with XP on it.

Pros on the iMac: beautiful, fast, runs leopard =)

Cons on the iMac: not easily upgradeable (if at all), apple doesn’t provide warranty in my country, pricey for my budget

Pros on the Custom rig: cutting edge, easily upgradeable, will last for years to come, lots of options and parts to choose from, cheaper than the iMac

Cons on the Custom rig: Windows, lots of cabling involved, windows

I’m a web developer, I love linux too but I need Windows or OS X to run adobe suite.

You decide the fate of what my next pc will be…