Message Edited by sjmaye on 12-27-200607:56 AM
I have read several relatable questions and had my own similar questions about adding add-on cards, external USB devices, and internal HDD's including Solid State SATA drives.
All suggested that I replace the factory build which was something like (approx. can't remember exactly) 250 watts/300 watts max. continues. Adding a graphics card upgrade, a SSHDD and max. RAM dim cards I went for a name brand PS (Power Supply) from EVGA w/a "Bronze" rating in its class of 500 watts which is what my budget barely allowed.
Most comments and PS calculators, (software you can find online or downloads) say to upgrade to at least 3-times the minimum calculated and don't be too frugal about cost.
You can't really over do it, the system will demand only what it needs but a good PS will also help protect the entire system from Power Surges which can and will happen, e.g. thunderstorm power surges, interruptions from unforeseen conditions like snowstorm outages suddenly causing stuttering power/on/off/on....etc.
Hope this helps.