HD4850 Running at Low Memory Clock

I recently built a computer with:

MOBO: BIOSTAR TA790GXB
http://www.newegg.com/Product/Prod [...] 6813138143

CPU: AMD Phenom II x4 940
http://www.newegg.com/Product/Prod [...] 6819103471

GPU: HIS Radeon HD 4850 1GB IceQ4
http://www.newegg.com/Product/Prod [...] 6814161245

RAM: 4GB (2 x 2GB) DDR2 1066 Kingston HyperX T1 Series
http://www.newegg.com/Product/Prod [...] 6820104098

PSU: Antec 380-Watt, 2x +12V rails, 1st one at 16 amps, 2nd one at 18 amps

Others: 1 80GB IDE HDD and 1 DVD Drive, 2 case fans

Everything is working great, except on both GPU-Z and CPU-Z it's only registering my video cards Memory Clock to be running at 993 MHz opposed to the advertised 1986 MHz.

I've checked it out during load and it always displays this number, despite the Core clock changing between 500 MHz and 625 MHz between idle and under load.

I'm not sure if this is just because these programs don't have placement for a 4th digit (although I wouldn't know why because I'm using latest versions) or if my video card really is running at lower performance than it should be. RAM is running at 1066.

One of my guessing was that the power supply (which I just had laying around the house) is bottle-necking the performance in some way, I wasn't even going to use it at first but when I tried it and the computer performed correctly even when playing demanding games, so I figured I'd stick with it. Could this possibly be the problem, or cause any kind of damage to my components?

at 1024x768 (monitor's max resolution ), on Windows XP Pro I can max out any game and get great results. On Crysis with very high settings (there was a guide showing me how to do this on Windows XP, I know your only supposed to be able to do it on Vista) I average 25-45 FPS.

Does it look like my video card really is not running as it should be and could my weak power supply be causing this or any other negative effects on my system?