ok. dunno how much stuff costs in NZ, but i'm going to tell you that if you're planning to impress someone...let alone ppl at a car show, you're going to be needing a little more money than that....unless of course you're going to be doing all of this yourself. =)
but for show purposes, try to stay consistent with parts. you can go all alpine, or all JL audio. judges like that. they liked my car. =)
OR..go with flashy stuff. LEDs and neons are always the best way to get kudos. pheonix gold amps have a nice looking format with LEDs. eclipes subs have a nice look and sound good as well. if you're strickly looking for good bass, you might want to look into JL, they got the punch.
maybe high end might impress a judge. then go with persion power. they're known for the best amps, though they're ugly....in my opinion. not much going on. hehehe.
something cool and clean. amps on the side, and mount a sub in a box facing out. it'll look real clean. or do a fiberglass kit and mount the sub in the wheelwell. that's always nice, and it sounds good too. always cool to channel the bass by cutting a hole in the back dash between the two rear speakers.
ok. those are MY ideas. hehehe.
check out my system in this forum. i believe the post is labeled "new system"