Inspiron 545 upgrade PSU

I recently bought a nVIDIA GTX 650 ti for my Dell Inspiron 545. It required at least 400w from PSU. My pc currently only have 300w, and i am looking at Antec VP450 http://store.antec.com/Product/power_supply-basiq_power/vp450/0-761345-23540-2.aspx.

I wonder will the Antec fit in my pc PSU slot or is it too big and i have to look for another one? Thank You all :)

And my current PSU is HP-P3017F3 by HIPRO