Please help me with graphic card compatibility

[Neftie]

Hello there!
(Please excuse my poor English)

I'm recently shopping for a new graphic card to replace my dinosaur-old ATI Radeon HD 3400.
My current candidate is :
http://www.amd.com/us/products/desktop/graphics/amd-radeon-hd-6000/hd-6770/Pages/amd-radeon-hd-6770-overview.aspx#2
(Radeon HD 6770 XFX Radeon HD 6770 (HD-677X-ZNFC) 1024MB PCIe x16 Gen 2.1 Eyefinity 6 Edition)

I would like to make the purchase soon but I want to 100% sure is it compatible with my computer, this is the first time I'm buying a graphic card so I'm pretty new at this and don't want to mess anything up, I would be really grateful if you guy help me out on this.
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My PC specs:
AMD Phenom(tm) 9550 Quad-Core Processor
2.2 GHz
Microsoft Windows Vista Home Premium Edition Service Pack 2 (build 6002), 64-bit
ATI Radeon HD 3400 Series (doesn't matter right?)
6.00 GB RAM
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For the requirement I noticed 2 pretty important thing:
*PCI Express® based PC is required with one X16 lane graphics slot available on the motherboard
*450 Watt or greater power supply with one 75W 6-pin PCI Express® power connectors recommended (600 Watt and two 6-pin connectors for AMD CrossFireX™ technology in dual mode).

I'm not too sure about the above so I opened up my computer and checked, I think I have the
16 slot for the graphic card, but it look a bit cramped so I don't know if it'll fit, as for the 6 pin PCI express I could't find any that look like the picture I googled, I took a couple of pic of the inside, please have a look -
(yes it pretty dusty I'm cleaning it as we speak!)
http://imgur.com/a/h5sDW#5

If the worst case that the card I choose is not compatible, could you guy recommend one for me ? ATI and around $140 budget.
I REALLY need to upgrade because I could barely use it for most real time 3D application, and games modern FPS game, ect. :\

Thank you everyone for your help and time in advance. : )

(If you guys need additional picture or spec/information please let me know)

 

[smorizio]

there shoudl be a service part number on the mother board or a model number if not run cpu-z and gpu-z. with cpu-z you get the model of your motherboard and we can look it up to see if the mb has agp or pci slots or pci-e slot. the power supply is only a 300w unit.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139027&cm_sp=Cat_Power_Supplies-_-Spotlight-_-17-139-027
here a good one that onsale..as long as it a good brand that 80 rated any 500w will have at lest one 6 pin pci cable. it in the last images about the power supply. crap power supply wont put out there rated power and can crash or pop and take out your motherboard.
http://www.youtube.com/watch?v=wK8p7dGSdmo

 

[akxpckwb]

Regarding the motherboard you're good to go. Just take the 3400 of and put the 6770 on the same slot.
Your PSU does not seem to have the required 6 pin connector however there should be an adapter like this http://bigbytepc.net/images/molexpcie.jpg on the same box as your new GPU.
The 6770 is a good card for it's price and you should have no problems with it on modern games however notice that your CPU is a bit old

 

[quilciri]

That's a 270 watt PSU. Use a 7750.
http://www.newegg.com/Product/Product.aspx?Item=N82E16814161403

Your PSU won't support a 6770. The 7750 draws all it's power from the PCI slot (no 6 pin), and only uses 43 watts at full load as opposed to the 100+ watts the 6770 can draw.

 

[Neftie]

Oh dear, so look like my PSU doesn't support it?
I just need a temporary replacement for a bout a year before I buy a completely new PC so I don't want spent money for additional component, only in case that I have no other choice.
Just need a good working card for my 3D project/work with deadlines.

Quilciri, thank you for the recommended card, I'm looking it up.
What do you guy think about that? should I get the 7750 instead then?

 

[Neftie]

Best answer selected by Neftie.