PSU upgrade question.

[Robby]

Here I am back with another topic similar to an older one, but w/e.

So I looked through some PC upgrading options, and found a quad-core CPU that'll pretty much suit me for now. First things first, need to change the motherboard since AM3 is pretty dead nowadays, so an FM2 will hold me for now. An Athlon II x4 740 (3.2GHZ, pretty much the cheapest quad-core in my area AFAIK, better than what I use nowadays, wouldn't be able to go higher than that).

But the thing that worries me, like the title says, is if a PSU upgrade might be necessary. I'm guessing so, considering I have a 450W PSU, with the following specs:

Spoiler below!

AMD Athlon II x2 250 (3GHZ DC)
AMD Radeon HD 6670 1GB DDR3
4GB DDR3 1666MHZ
1 DVD-RW drive
1 Case fan
1 fan on the CPU and another for the GPU
6 USB slots on the back of the PC.

There might be some things missing from ^, so lemme know if I missed anything.

But yea, is a PSU upgrade necessary, and if so, how much would I need to go for? Planned for a 600W PSU which is less than $30 over here.