Every montherboard I have had after KT133 era has shown low 5V and 3.3V and Ive tried diff PSUs I have... My Enermax 330W... 400W... Antec 400W... all had low voltage readings. As long as the 5V isnt under 4.6 and the 3.3 isnt under 3.15ish you should be fine. My Enermax 400W and A7N8X sit at about 4.76/3.21 and its perfectly stable. So I wouldnt worry alot about it. The last 4 MBs Ive had (With 3 different PSUs) all were low.