Currently looking at building myself a new machine, here's what I'm specing
CPU, definitely go Intel dual core 2 at least E6600 as this starts the 4mb cache.
Mobo, minimum spec
My choice here is Asus P5B
RAM - 2Gb Corsair PC8500 DDR2
Video - Gigabyte 7950GX2 1Gb, 2 cards SLI'd together
HDD - HDASEA1103 (ST3500630AS)
Seagate (ST3500630AS) 500GB SATA II HDD - 7200RPM, 16MB buffer
This is obviously a very high end spec and will probably be about AUD3K (THB85K).
When I was living there, the newer top end parts where difficult to obtain, I hope things have changed.
I used to use BUS at Big C (recommend) and U2 up past Lotus, but they were abit over priced.