450w power supply enough?

You'l need something like 600W. 450W is running very low and leaves no room for upgrades, overclocking or possibly even powering what you have. If you intend to Crossfire later you'l need a 750W.

if it is a quallity brand and has a strong +12v rail like Antec, Silverstone, Corsair or Seasonic - yes. Any other 450 W PSU probably not, especially if you want to OC that IVY. but you would likely limit you expansion options.

I have a i5 2500K on a HD 7850 on a ST45SF in my HTPC Gamer box. Not over clocking it yet though, but I am sure it will handle it.

without going into detail on the different voltage and such a good rule is 80% of max power so on a 450W PSU you have about 360W useable. (secondary consideration would be the strength of the 12V rail)

typical system OC'd i5 Ivy = 208W without GPU running Prime 95
GPU HD 6770 = 108 w (not over clocked) running Metro loop
Total 316W leaves only 34w to spare

you should use a really strong 500-600 W PSU if you are planning to OC that Ivy and want to maybe upgrade your GPU later.
Antec, Silverstone, Corsair or Seasonic.

I currently own a CX430 V2 and it powers:

i3-2100
2 X 4GB Ram
H61 Mobo
DVD Burner
500GB HDD
OCed 6850

A Quality 450W like the XFX one or the Corsair , Antec , Seasonic will be more than enough for those req above..............

Just plug it in ...it should work fine

As previous users have mentioned; you'll be fine with a 450 watt Power Supply IF it's manufactured by quality companies such as Corsair, XFX, Seasonic, etc.
However, I would recommend you getting a 650 Corsair Power Supply because;

1) It's only about $25 more
2) Power Supplies are more power efficient at about 60-70% load [basically, you'll earn that $25 back in energy savings in about an year]
3) you have a very very capable CPU - if anything, you'll want to upgrade your Graphics Card [or CrossFire] about a year down the road and this 650W Power Supply will keep your options wide and open.

Corsair 650Watt Enthusiast Series [Version 2]
http://www.newegg.ca/Product/Product.aspx?Item=17-139-0...

~Coffee

The OP's configuration is going to be around 250W max sustained load so a good 450W PSU with 80+ Bronze or better rating would be more power-efficient than a 650W PSU of similar quality operating at under 40% load.

I was mainly wondering because my current build uses a coolermaster gx 450w psu

http://www.coolermaster-usa.com/product.php?product_id=...

should I use that or shall I purchase a more powerful one 650-750W one?

Your current power supply is sufficient for now; you don't have to get a new one now. You can always buy one when you decide it's time to upgrade your graphics card or getting a second for CrossFire.

~Coffee

your old PSU should be fine, it is one of the few good PSU's that CM stamped their name on.
http://www.hardwaresecrets.com/article/Cooler-Master-GX...