Power Supply Failure 2 in row?

Hi folks,
I recently upgraded my PC and im getting terrable problems with Powersupplies. The one that i had was a good brand and make or so i thought the Corsair hx 620 Watt. I had my PC setup all cables connected properly and nothing...eventually i found out that the Previously working PSU was dead. It cost me quite alot at the time back in march. Only got an RMA number today so its gonna take a while to get a new one.

Anyways so i go buy a new one in the meantime a 600 watt "Artic Jeantech" which i must say looks cheaply made and sure enough all cables connected and nothing PSU dead again a brand new one.

Now either im stupid or terrable unluckly. And yes im wearing static protection. Ive never had problems like this before with any PC Upgrades can anyone help.

The motherboard i have is a good make and i paid almost double so it would be of good quailty its a "Gigabyte MA790FX-DS5".

Ice checked both power supplies with the "Paper clip" method and there completly dead. Ive tried plugging them in with other cables and in different sockets around the house.

The amazing thing is that the motherboard CPU and everything connected to it atm is running on a 450 Watt Jeantech PSU. Which i had kept as it has a problem in that it just turns on the mobo. This piece of crap PSU should be in the Bin but its running things atm. I know its not powerful enough but its all i have atm until i get another new PSU tommrow.

So am i unlucky or is something wrong somewhere?

AMD Phenom 9850 (64 X4)
Gigabyte MA790FX-DS5
4 gigs DDR 2 PC 6400 ram
ATI 4870 512 mb PCIE
WD 1TB Western Digital SATA 2
Emprex DVDRW
120 Samsung IDE
400 Samsung IDE
250 Samsug IDE
Conceptronic SATA/IDE Combo Card
2 System Fans

and of course;
450 watt Jeantech PSU

Is it possable that 600Watts is not enough for my setup? And if so how come a crappy 450Watt PSU can keep things running?

Whats causing the PSU's to Fail? Was i just unlucky?

I highly doubt that generic PSU can have enough juice for this machine.