the tier something. im using a aerocool strike x 600 watts which is in tier 4 of the psu hierarchy here in tomshardware and is considered to be replaced immediately. so far no issues for me.
well that is up to you if you want to replace it to a more trusted brand like thermaltake, evga, corsair or xfx.
all in all that 450 watts will be enough to run it.
and by the way i used to run a gtx 650 ti boost on a korean true rated full sleeved 450 watts psu (powerstation 2 450 watts blue) and i got no issues and whatsoever encountered.