How to test a motherboard? PSU Reccomendation.

Ok :help: so have an ASUS A8N SLI 939 board the chipset fan started whining but i monitored the temp, put a fan to blow directly over it etc and ordered some new fans temp never went above 40oC. Installed a new hard drive and all was working fine, until system freezes then on every reboot froze before getting to the first XP Pro loading splash screen, starting in safe mode etc it did the same.

Checked all cabling and disconected all but primary hard drive to see if that would help... it didnt.

Ran a few tests using Hirens Boot CD, but nothing showing as obvious, running extended tests in most things led to it freezing sometimes.

Left off over night, switched pc on with side door off and saw the PSU spark and some smoke an a few pieces of charred plastic come out. Its an EZCool 550W, with a supposed 32Amp 5V. Its never given me any probs and has been on almost 24/7 for 2 years.

I opened the PSU to check the damage, it blew something i can see where its scortched the PCB board and possibly blown some component. It also blew the power kettle lead fuse as far as i can tell.

I think i read somewhere that if i was to get a new PSU and connect it to the MB and it was dead that it would kill my new PSU. I'm looking to get a decent £60 PSU of better quality to cope with the 3 hard drivers etc (spec below) for the new few years.

MB is still under its 3 year warranty and could possible be sent back because of the chipset fan if i said i wasnt willing to fit a new one myself, and i'd get them to test it etc. But not ideal.

Also i need to know what PSU rating to get, i know the cheap ones like my EZCool the wattage and current drops after use, and i know this is what could have cause the overload or freezing in the comp.

The spec is;

ASUS A8N - SLI SE 939
AMD 3700+ Artic Cooler 64(to be upped to a X2 4600 or whatever at latter date)
1Gb Crucial Value Select (2x512Mb) (to be upped to 2Gb at some point when upgrading processor)
2x250Gb Samsung SATA Spinpoint HD
1x500Gb Samsung SATA Spinpoint HD
1x 6600GT Graphics (to be upgraded at some point)
1X PVR Card
1X LG DVDRW/RAM
1x LG DVD
1x 3.5" Floppy
1x Zalman Fan controller
2X120mm Fan
2X80mm Fan
1x250Gb WD External HD 3.5" External power
1XWebcam
1XWireless desktop
1XPrinter
1Xipod dock
1x5.1 Speakers
1xWacom Tablet

Thats about all i can think using any power, i use USB keys etc, and sometimes have 2 displays hooked up.

Thanks