Originally Posted by logray

A used engine is the cheapest route and will cost between 6-10k.

Tearing the engine down and having the cylinders fixed will cost minimum 6/7k DIY (4k alone for the larger bore), assuming that is the only problem... having a shop do it will be in the 15-20k range.

Used engines

http://www.flat6innovations.com/shop/home.php?cat=394

Sleeving

http://www.lnengineering.com/boxster.html
"In either situation, we can upgrade your engine to use our Nickies™ as long as there are no cracks in the case that protrude deeper than the bottom of the water jacket, where in that case, the integrity of the whole crankcase has been compromised! (see below). If the damage on the crankcase side, the damage is not repairable."