After seeing you model, you are good to go. I myself run a quad core phenom, 2-12 mm fans, dvd drive, 12mm-heatsink\fan, hd2600 ati g-card, two drives, 1 tb sata, 1 backup pata and have used my 450w PSU just fine, however, I am going to upgrade to a Corsair 750W soon due to "Holiday Gifts" of hopefully a nice Graphics card...
And as stated, if you are upgrading, then yes, you will likely need a larger PSU.
Many "good" cards require at least 500 or better, but that really depends on the card you need or if you ever get for that matter, the card will typically show the specs needed to run it.
So if ever the case you do decide to upgrade, I myself, for the price difference, would go with a bit more watts with a PSU so I don't have to worry about upgrading in the near future. When it comes to power supplies, I feel it's better to have a little more than "not or just" enough and 500W is what I typically suggest, once again, depends highly on the system.
Currently, you are just fine.