[new System Homebuild] A request for Help From Chile

Hi, I wanna buy a new pc but only have 250000 CLP (Chilean money) & Need all less Screen and VGA, the VGA come later. my cotisation was.

COTIZACION 10.08.2009 @00:12hrs SYM Computación - http://www.sym.cl
#288 1 GIGABYTE MA78GM-US2H AMD780G SOCKET AM2 4DDR2 VID-INC PCIe (Stock agotado) $59.310.- ($56.344)
#121 1 CPU AMD PHENOM II X2 550 3.1GHZ DUALCORE L3 6MB AM3 BLACK ED BOX (Stock normal) $81.301.- ($77.236)
#493 1 DISCO DURO HITACHI 500GB SATAII (Stock normal) $41.317.- ($39.251)
#301 1 MEMORIA DDR2 KINGSTON 2GB 800MHZ PC2-6400 (Stock normal) $19.992.- ($18.992)
#162 1 TECLADO GENIUS KB-06X ESPAÑOL BLACK (Stock normal) $3.998.- ($3.798)
#937 1 MOUSE OPTICO MICROSOFT 3B BLACK (Stock normal) $7.997.- ($7.597)
#550 1 REGRABADOR DVD LG GH22NS50 FORMATO ± DVD R 22X SATA OEM (Stock normal) $18.926.- ($17.979)
#7052 1 GABINETE ATX TREETOP PORSCHE TC-D302 (SIN FUENTE) (Stock bajo) $15.994.- ($15.194)
#4013 1 FUENTE DE PODER NJOY 650W ATX 24 PINES (Stock normal) $10.662.- ($10.129)
---------------TOTAL---------------
$259.496.- $246.521.- (pago contado)

and my questions are:

can I put this AM3 proce on a AM2 Motherboard?
the Power source will work on this pc?
the power source can hold a future hd4870 VGA?

sorry about my english and Thanks!

Power supply is okay.

ATI Radeon HD 4870 System Requirements

500 Watt or greater power supply with two 75W 6-pin PCI Express® power connectors recommended (600 Watt and four 6-pin connectors for ATI CrossFireX™ technology in dual mode)
Certified power supplies are recommended. Refer to http://ati.amd.com/certifiedPSU for a list of Certified products.

http://ati.amd.com/products/radeon [...] ments.html

You probably want 4 GB DDR2-1066.
Gives you overclocking room.

thank to all guys. I will change the power suply

$40 bucks

that's like 28000 CLP ..

thanks a lot..

now I'm more sure about my build.