I need serious help for with my HD 3850

[GER]

I have a Gecube hd3850 512 GDDR3 NOT overclocked version, the default core speed is 670mhz and memory speed is 700mhz (is that normal or too low?)
It delivers crappy performance, my 3dmark06 score is like 5100, today is was playing Red Alert 3 it run very smooth on the High preset settings, but when i turned it up to ultra high 2xAA the fps drops to like 12!! Stalker Clear sky runs as low as 3-5fps (even with the latest catalyst driver 8.11 and the hotfix).

i tried to overclock it with the default catalyst, it would let me, the bars don't even move. I uninstalled catalyst and tried Ati-tools and Rivatuner but the sliders automatically return back to the default clocks.

I suspect this being because of four possible factors:
1- low wattage on the card , i have 400w psu with 12a on the 12v rail (if you want, this link elaborate my power state exactly http://www.hardwareforums.com/should-i-get-new-psu-my-hd3850-23947/#post141635)
2- not much RAM ( i have 1gb maybe i should put 2gb)
3- my card is faulty.
4- mu CPU (pentium D 925 Presler) is not able to keep up with the card thus the low fps.

Please help me figure out my problem, because i am worried about buying a new PSU and more RAM etc. and then finding that the performance is still like crap.

 

[GER]

I took my PC today to upgrade the RAMs, (because i suspect the cause to be mainly about the PSU and the RAMs), so the store owner told me that my problem lies in my motherboard and CPU (Intel 945g and Pentium D 925 Presler)and i have to change them; I am now confused and depressed I wanted to actually throw that rig out and buy a brand new one, but what really pisses me off is that it's only one-year old, and when I bought it (another store) the guy said that this is the best hardware availabe today, clearly he was yanking my chain and i fell for it.

Now according to this new guy my CPU is a knock-off ! he told me that a year ago the 4MB cache pentium D 3.0Ghz CPUs weren't even produced! so he suggested a core 2 duo for $90 and intel P31 board for $80 saying that these will make the most of my VGA and that i DON'T have to replace my current PSU (the 12A PSU).
Is he just going for making a sale, I mean the CPU might be a factor but is my board BIOSTAR really not able to handle a HD 3850 ?!?


I am upgrading the RAMs to 4GB either ways but PLEASE, PLEASE, PLEASE enlighten me of how to make my Hd3850 work as expected; should i upgrade just the psu ?, or keep it and upgrade the board and cpu as he emplied ? i am getting desperate.