Adcom GFA 555 amp upgrades

Hi. I own an Adcom GFA 555 amp, and I'm wondering if its practical to upgrade the amp to the standards of the Adcom GFA 555 series II (or better). Love the power and flexibility of this amp, as it powers my 4 ohm Kef Reference 103/4 towers with ease, but you know how it is, we audio junkies are always trying to squeeze a bit more fidelity out of our gear. Many thanks! -David