Is my 450w Psu good enough for AMD 6770?

Hey everyone, this is my first post here!  

So i was thinking of buying a 6770, because my current radeon hd 5550 just isn't enough for my needs... before i buy the new card however, i would like to ask some of you guys for advice  . My psu is a 450w and it has 26 amps ( 2 +12v rails ) . The rest of my system is as follows :
Intel dual core e5400 @ 2,7ghz.
4gb ram
750 gb harddrive
and a Gigabyte Mobo with pcie 2.0 (it works with 2.1 cards too right?)

So would you guys recommend that i would buy it, since the rest of my system really isnt that power hungry. I'm not planning on buying a new Psu right now, maybe in a month or so.

Any feedback appreciated,
Thanks.