If it's not giving you problems, then it's sufficient enough it seems.
I have 350 watt 3.3V@24A, 5V@28A, 12V@12A powering:
P4 2.6@3.06ghz
2x256mb of RAM
2 HDDs
2 DVD drives
4 case fans (1 LED)
1 light tube
It's actually not too bad, but I have to clean the power supply once in every 6 months or the dust inside results in poor heat dissipation and my 3.3 v rail drops too low. Otherwise it's doing OK.
I wouldnt worry too much if you've had this power supply for a long time and it hasn't given you any system crashes or reboots.
Since you've had it for so long, you might want to open it and clean all the dust out of it (your warranty is probably up anyways).