Looking for a price check on the last 24" iMac with FW 400. This is the model here:

iMac (Early 2008) - Technical Specifications (http://support.apple.com/kb/SP485)

The upgrades include

• 3.06GHz Intel Core 2 Duo
• NVIDIA GeForce 8800 GS w/ 512MB GDDR3 Memory
• 500GB Hard Drive

Six months of Applecare remaining.

this may help you add some for the higher cpu

http://www.ehmac.ca/mac-desktops/81813-24-imac-aluminum-2-4ghz-intel-core-2-duo-se-oakville.html