Don't worry about the IMS. its not as common as its made out to be. I've been doing lots of research into the 987 Boxster and the 996 911 as i'm looking at buying in the new year.

From what i have been reading on the Porsche forums only around 5-10% have had experience with IMS failure. Its not a big cost though to have it swapped for an up-graded item. An american company do a kit for about $800.

Have an independent inspection done by a specialist prior to buying. this will highlight and potential problems.

I'm looking at either getting a 2000-2001ish 996 convertible or 2005-06 Boxster. I want to drive both first.

Insurance is cheap also. The Boxster for me and the wife is only £550 FC. thats £30 less than we are paying to insure the Wifes 05 Mini Cooper lol. The 911 is only £650 FC.

Cheack out Boxa.net and 911uk.com These were recommended to me on here and are great for info and seem friendly.