I have been on this cross road for some time as I want to build a new system.
Which will perfom the best on this enviroment?
The Opteron Quadcore or the Phenom II X4?

My guess was that the Opteron will, but I want to know your opinions and suggestions as to which I should buy.

what environment?

What are you using it for?

In most cases the phenom II X4 is your top option.

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AMD phenom II 1090T @ 4.23 Ghz custom water cooled
Asrock 890 FX deluxe 3 mother board
4 GB DDR 3 1600 @ 1688 Mhz 7 7 7 24 T1 2688 Mhz NB
2x 1 TB WD Sata III 64 mb cache HDD,s raid 0
2x 5870 HD @ 1015/1300 Asus reference
Dual OS win 7 x64 ultimate & win 7 x32 Ultimate (bench os)

Dual Boot.

Boot 1. Music Production DAW with a lot of plugins.
Boot 2. Video and Graphics

Basically Opteron and Phenom are the same core, and in most cases, clock for clock, they will perform the same.

The big difference between the processors is the certifications and duty cycles. Opteron is certified for windows server, linux server and enterprise apps like SAP and Oracle.

Opteron is specified for a duty cycle that is 7x24 for 3-5 years and higher utilization. Phenom is specified for a more consumer-like duty cycle (don't know the specs but it is more like 5x10 for 5 days a week or something like that.)

Austinbike,
thanks a lot. I didn't know all these before.
seems like the Opteron will be best for me.

But one more question.
Dop you think having 2p 4p configs will work well for music? I guess all the mobo manufacturers like Tyan say specifically that those boards ar for servers, but I need same for worksattion to run music programs like Cubase and Nuendo.

4P for music is definitely overkill. 2P might be. Check with the software manufacturer or other users to see how threaded the application is. In many applications if you aren't getting good threading then you have cores sitting idle.