SK-1 READ the fine print carefully is says'"......in conjunction with a 450 ....."; psu, not by itself. The 250 is to power the ATI card only while the 450 powers the othe components. The problem is once again the difference between total power output and the output of the 12v rail. Call ATI, but take your time, quiz whoever you get about the specifications on your graphics card box and eventually you will get the right answer once they realize you can read and are not going to leave them alone until you get an accurate answer. For example My ATI manuel says I need a psu with a 12v rail amperage of 32 amps. However this is only true if I'am using two cards in crossfire mode. For one X1900XTX, the minimum requirement is only 18amps. Most psu manufactures only list the total amp output of their PSU's. ATI's specs on their boxes are all different and non match the PSU's manufactures. It was all very confusing and I actually purchased 2 different PSU's before installing one in my rig. But that was after the long telephone call.
Also you will notice the output of the thermaltake 250 is 21 to 25 amps. Thus compounding the whole power requirement confusion. This PSU was not available when I bought my card, made my call to ati. I guess the best thing to do is call ATI and do what you believe is right. I also have problems with the tech support section of the company I work for, keep in mind they are basically taught to make the customer happy, regardless of the facts, and most of them are reading out of a programmed text answer book (funny pages). Good Luck