for a newbie, i think 20 thou with head unit is doable, especially if you take the time to scour the classifieds in kotseaudio.com.

you can get a good branded second hand 4 channel amp for about 6 thousand. brand new separates of reputable brand will cost you abot P4000. a targa sub will cost maybe P2500. you can probably get a decent headunit for 6,500. that leaves you 1000 for the installation and sub box. medyo kulang, but then again, you might be able to save some money on some components. i think 20 thou with head unit can be done and even 15 thou without head unit is achievable.

on my galant, i plan to use my 4 channel amp (resale value P6000), a pair of 8 inch targas in the rear deck (2k each?) and a set of 3 way targas (P3000 ata) total is only 13 thou. not boom boom, but good enough for me. dumaan na kasi ako ng boom boom

andy