no, i havent bought it yet, just making sure i can upgrade safely with no loss of functionality to my comp. I checked ATI HD 4350 specs which stated that the card needs:
300 Watt or greater power supply (350 Watt for ATI CrossFireX™ technology in dual mode) is recommended. I have 305 watts, so am i good to go!?

so am i good to go!?

I don't know. I don't know what extra hardware you might have in there. I also don't know the current requirements of the card, or the quality of your current supply. I was not able to find a copy of the manual for that card to download either.

I recommend you run through the calculator above. Note that providing good, solid power to your computer is very important. If you have any doubts about your current supply, you should probably upgrade.

Had a look at the PSU calculator, but some of the lists i wouldnt have a clue if i have them, eg,cold cathodes, or capacitor aging? When i put in what i know i have, it calculated 279 watts.

I was looking at the card: Gigabyte HD 4350 512MB GDDR2 VGA DVI HDMI HDCP PCI-E Graphics Card
Its using ATI Radeon HD 4350 which needs a minimum of 300watts according to AMD. So if ive 305 watts and potentially needing 279, is to to risky to go ahead, i mean it the gao to small?


Specs:Product Specifications
General
Device Type Graphics adapter
Enclosure Type Plug-in card
Interface Type PCI Express 2.0 x16

Processor / Memory
Graphics Processor / Vendor ATI Radeon HD 4350
Clock Speed 650 MHz
Video Memory Installed 512 MB
Technology GDDR2 SDRAM 64-bit
Memory Clock Speed 800 MHz
Features Avivo HD Technology, ATI CrossFireX Technology, ATI PowerPlay technology, Ultra Durable 2

Video Output
API Supported OpenGL 2.1, DirectX 10.1
Digital Video Standard Digital Visual Interface (DVI), High-Definition Multimedia Interface (HDMI)
HDCP compatible Yes

Expansion / Connectivity
Interfaces 1 x DVI-I (dual link) - 29 pin combined DVI ¦ 1 x HDMI - 19 pin HDMI Type A ¦ 1 x VGA - 15 pin HD D-Sub (HD-15)
Compatible Slots 1 x PCI Express 2.0 x16

Miscellaneous
Certified for Windows Vista Certified for Windows Vista software and devices have undergone compatibility tests for ease-of-use, better performance and enhanced security.
Compliant Standards RoHS

I indicated what to set aging at. If you followed the instructions I gave and it comes in at 279, then you are probably fine, IF that current supply is running fine. But, you first said this card was the 1Gb version, not 512Mb. That means it will need more power.

I personally think your attempt to avoid buying a new PSU ia the wrong course to take. High speed digital electronics need quality, stable power. You are pushing the limits of the PSU in any case so I would suggest you just plan on buying a new PSU.