The best power supplies, in my opinion, are from Corsair or Silverstone. That X1650 XT is from 2005, why be obsolete from the beginning? If all you want to do is listen to music, you don't need a powerful PC. Something like the EVGA 512-P3-N944-LR GeForce 9400 GT, which was released in 2008 and requires a 300W power supply, would be a great alternative.
I dunno, I would not use a video card that would max out the power supplies. those bestec power supplies are decent for average computer use, but if you put a video card in that requires a 300 watt power supply it is going to strain the poor thing, and they were never designed to be put under that kind of stress load and chances are it will shorten the life of the Power supply. theres nothing wrong with the PSUs if you use them for what their designed for-same with most prebuilt computers, but manufacturers, in order to cut costs put in the most generic, run of the mill power supplies, and were not designed for major upgrades in the future. yes, the 9400 and even the card I recomended, will run on them but they will put a lot of undo strain on the power supply and cause it to die much sooner then it should, and running under load it will also heat up and heat up the rest of the system, and heat can also damage other parts. I would stay with the 1650 with that power supply, any newer and a I would recomend a new power supply, even if its a 450 watt okia off of ebay.