I'd personally get this one instead:
http://www.shopping.hp.com/webapp/sh.../e9300z_series
You'll save $100 and you won't notice a huge slow down in apps or games.
Benchmark to prove my point:
http://www.anandtech.com/bench/default.aspx?p=106&p2=52
Like Bryan said, the 4650 will run on that PSU, it's proven to work on crappy Dell PSUs and the 300W HP PSUs.