Thanks, a little kext tweaking and I got 10.5.8 running. Issues: Audio - speakers only, no headphones. Wireless - unencrypted 802.11g only. Built-in Webcam Fingerprint Reader Good: Everything else. Only sees half the ram of the gpu - but I have all the graphics acceleration enabled and working flawlessly. Word of Caution - ALWAYS backup your kexts prior to updating via Apple. Thankfully I did.
Find a college student with extra cash from mommy and daddy. That's what I did, 24 months after I built the machine. Got every red cent out that I put into it. Then again, I had built a custom Shuttle - with all the bells and whistles. Seriously, college students who spend someone else's money aren't going to haggle you as much as someone who actually worked for their own money. Who knows, you might get lucky. Good luck!