A good PSU is the Zalman 600W PSU. I have it myself and it's great, really quiet thanks to the passive cooling! And it's modular too, though they have a lot on those cables and my case is basically filled thanks to the pci-e connectors, sata power, ide power, all my fans..
Also you shouldn't worry too much about the heat, i don't think you'd be overclocking this as it is your working computer. Airflow is good, i hardly see any cable hanging in there ;)