i've been going around too for a new HU. the cheapest one that i saw na branded is a sony xplod at 4200 pesos. CD lang sya, walang MP3.

for non branded units, the cheapest one i saw is a china made one (nakalimutan ko tatak) at 3k. mp3 capable na din.

proline, i think sells for 3.2k. may Aux, USB and MP3 na.