1)Most AMD boards support 955BE even if it wont, then there will be a bios update by which this isssue can be solved.
2) To OC CPU bios is helpful,for GPU there are various softwares like after burn and most GFX are bundled with software.
3)Yes you can use INTEL DH67BL B3 board to use Ivy Bridge CPUs.
4)Just speed no performance benifit.100MHZ difference and that isnt notable at all.
5)No you wont have any issue as i too have a mATX borad as i have no issue.But your cabinet might cause some issue.
As for Corsair CX 600w V2 1 thing i will say,it has got only 3 years warranty against that of Seasonic with 5 years warranty.
And Seasonic can do much higher than what it is rated.
As you wouldnt be OC the below config would serve you well
CPU- Intel i5 2400 -
TheITWares - One Stop for all Gizmos!Intel Core i5 2400 Sandy Bridge 3.1GHz (3.4GHz Turbo Boost) 4 x 256KB L2 Cache 6MB L3 Cache LGA 1155 95W Quad-Core Desktop Processor BX80623I52400
MOBO-
TheITWares - One Stop for all Gizmos!Intel DH67BL LGA 1155 Micro ATX Motherboard
PSU - seasonic s12II 520(As you wont OC)
TheITWares - One Stop for all Gizmos!SeaSonic S12II 520 Bronze 520W ATX12V V2.3 / EPS 12V V2.91 80 PLUS BRONZE Certified Active PFC Power Supply
In this intel mobo as you wont be OC at all so seasonic s12 II 520w can handle the config with GFX like GTX 560Ti/HD 6950 at stock settings.
If you are very much interested to OC or want to know about OC and to play with it then AMD is the the only way .
If so then get the following
AMD-phenom 2x4 955BE
Mobo -Gigabyte GA 880GM USB3
PSU- seasonic s12II 520(only if GFX is HD 6850 and Also for GTX 560Ti/HD 6950 if not intended to OC CPU and GPU)-
TheITWares - One Stop for all Gizmos!SeaSonic S12II 520 Bronze 520W ATX12V V2.3 / EPS 12V V2.91 80 PLUS BRONZE Certified Active PFC Power Supply
PSU- Seasonic s12II 620(If GFX is GTX560/HD6950 And if you OC Both GPU and CPU) -
TheITWares - One Stop for all Gizmos!SeaSonic S12II 620 Bronze 620W ATX12V V2.3 / EPS 12V V2.91 80 PLUS BRONZE Certified Active PFC Power Supply
If you are getting GFX like GTX560Ti/HD6950 then get 620w ,as it would help you OC both CPU and GPU.
And 520 is recommended if you are getting GFX like 6850 then 520 would be OK for OC 955 BE +HD 6850.
Ram -As you wont be OC get Coarsair XMS3 1333mhz 4gb- 1250/-