my buget depends on the good will of my parents and i dont know how much they want to spend so i was just having a look my budget could be less than 1000€ or more
Well, then forget SLI. Thats only for the very high end systems with monitors with more resolution than 1600*1200. The new 8800GTS and 8800GTX in single card configuration are much more powerful than older cards in SLI and the 8800's in SLI is insanely expensive.
But for 1000€ you have enough budget for Core2 which is much better than anything AMD has today. As you are talking euro, I suppose you are in Europe. Here in Denmark I just bought a system for 1200€ (excl. VAT) which I would recommend for the price:
Intel DP965LTCK motherboard
Core2 E6600 (2.4GHz)
2 GB DDR2-800 (Kingston KHX6400D2K2/2G)
Antec P150 case with NeoHE powersupply included.
White Alps floppy drive
320 GB Seagate 7200.10 SATA harddrive.
DVD+RW drive LiteOn LH-18A1H-483C, White, Bulk
Graphics card MSI NX7900GS-T2D256EZ, PCI-E, 256MB
Monitor LG TFT 19¨ L1952HQ (has DVI).
Notes: This is a excellent allround system optimised for moderate gaming performance and silent operation. RAM and motherboard has not been selected for overclocking and the powersupply and motherboard won't allow SLI (which I don't recommend anyways). If you want more gaming performance, then substitute the passively cooled 7900GS for a 8800GTS. If the 1000€ is the budget, then subsititute a E6300 for the E6600 or use a used CRT monitor instead of buying a new LCD.