thge pheonix digital...shit. Even the manufacturer fails to list the THD rating at ratedn power. Any amp can produce that much power. However, what comes out won't sound like music.
The MTX...slightly more power than the Alpine's RMS. Alpine is a better brand though, and while I didn't check, im certain the THD and S/N ratio are lower/higher on the alpine.
The Pheonix Gold is also ok. It has slightly more power than the Alpine, but a slightly higher THD. The S/N iss higher on the PG, which is also good. It basciallty comes down to what you want size wise and volume wise. The Alpine is the best amp with the lowest THD, but being so close to the the PGs THD the higher S/N may come into play at higher volumes (110dB vs 100dB on the Alpine) makin it the better. If nothing else, choose on size. The alpine has less of a footprint.
<span style='color:gray'><span style='font-family:Courier'>1995 e36 3 Series RIP
1999 e46 3 Series BURN IN HELL
2000 MR-S Roadster= Current</span></span>