Dual nehalem build

Hi everyone,

so i wanted to build a xeon nehalem for arch vision with 3ds max , and i folowed two forums on this site to specify my specs
so here they are

Case : COOLER MASTER
http://www.newegg.com/Product/Prod [...] 6811119138

MOBO : SUPERMICRO MBD-X8DAi-O Dual LGA 1366 Intel 5520
http://www.newegg.com/Product/Prod [...] 6813182186

Power supply: CORSAIR CMPSU-750TX 750W
http://www.newegg.com/Product/Prod [...] 6817139006

Processor: Intel Xeon E5520 Nehalem 2.26GHz (2x)
http://www.newegg.com/Product/Prod [...] 6819117185

Memory: Crucial 6GB (3 x 2GB) (2x)
http://www.newegg.com/Product/Prod [...] 6820148259

Hard Disk : Western Digital VelociRaptor WD1500HLFS 150GB 10000 RPM
http://www.newegg.com/Product/Prod [...] 6822136296

Hard Disk: Western Digital Caviar Black WD1001FALS 1TB 7200
http://www.newegg.com/Product/Prod [...] 6822136284

Video card: SAPPHIRE Vapor-X Radeon HD 4870 1GB 256-bit http://www.newegg.com/Product/Prod [...] 6814102825

CPU- cooler: Dynatron G666 60mm Double Ball Bearing CPU Cooler
http://www.newegg.com/Product/Prod [...] 6835114086

Display: ASUS VH242H Black 23.6"
http://www.newegg.com/Product/Prod [...] 6824236052

Arctic Silver 5 Thermal Compound - OEM
http://www.newegg.com/Product/Prod [...] 6835100007

LOGISYS AD202 12V Molex to 8pin P8 Adapter – Retail
http://www.newegg.com/Product/Prod [...] 6812887002


so we put it together and then
nothing would lit. the fans would spin for half a second and then nothing.
so we twitched the molex cable and then everyting lit up

only the screen didn't, but i read in a post that the supermicro boards could take a minute to post so i waited A WHOLE NIGHT. in the mourning stil no signal. so the screen was still out.
no beeps, only lights (video card, led, mobo)

so i removed the memory to see if i would get a beep but still nothing. i then left it on, thinking of the slow startup and went away for 5 minutes, and when i returned ONLY the mobo ligt (green light was lit). and sinds then thats it.
i was thinking it could be the power supply and buying another one which doesn't need the molex for powering 2 cpu's
i want to know your opinion, and what i can do to resolve this.

QUESTIONS
1: do i need another power supply which will power 2 cpu's without molex, and which would do.

2: did i buy the right cable (molex to 8 pin) or do i need another one

3: what could this problem be

so i thougt i would like to have a machine which also has the possibility to play games
and as far as i know 3ds max doesn't demand as much from your gpu.
so thats why i made the decision.
but do you have any recommendation for a good psu
please sent a link