DAC-15 media converter vs. DecklinkSP

My DAC-2 DV-Analong component converter is giving up the ghost. Thinking about the DAC-15 to replace it, or moving from my G4 Quicksilver Dual 1's to a MacPro with a BlackMagic DeckLinkSP.

A) Quick fix plug and play with hopefully better encoding than DAC2, or B) Major upgrade of platform, hard drives to get the "best" quality. Any tech guys out there run a comparison test between the two?

Thanks for any insight.

Carlos