I appreciate so much all of you giving advice in this dilemma. Love you guys! 

I have finally found a machine with a decent price but am not sure if it is ok. Here are the specs:

Intel Core 2 Duo
E8500, 3.16Ghz, 1333Mhz, 6MB Cache
Motherboard: Gigabyte GA-EP45-UD3P
Ram: 4GB
Type of memory: 2 x 2GB A-Data DDR2 800Mhz, PC-6400
Memory slots: 4 + 2 available
Drive: 640GB Western Digital Caviar SE, 16MB Cache (S-ATA II, 7200rpm)
Graphic card: LeadTek GeForce 9800GT, 512MB
Optical: Samsung 22X DVD±RW DL, S-ATA
Audio: 7.1 Realtek ALC889A
Windows Vista Home Premium 64-bit
Power: 450W Corsair CMPSU-450VXEU

Approx. US$ 1275