Weird E510 Issue - Need Advice

I have a two year old E510 that is having some issues.  It's out of warranty and needless to say, Dell don't want anything to do with it.  The trouble started about 3 months ago.  Initially, the PC would simply freeze or reboot after several hours.  Then after a day or so it would just loop through the boot sequence, randomly restart at different points, and then repeat the cycle.  After another day it would just die and the power light flashed yellow.  If I tried to start it a few times it would make strange arcing sounds and the power light would flicker until I yanked the power cord.

 

Because I was on the verge of a big move across country, I had a certified Dell repair shop take it in for a look as I didn't have time to mess with it.  The guy determined (and I agreed) it was the power supply.  He replaced it with the stock Dell PSU for the E510 and I ran it with monitor, mouse, keyboard for the next 48 hours just to be safe.  It seemed fine and I packed it for its ride in the back of the moving truck.  I didn't see it again for 3 weeks (long story - totally irrelevant).

 

When I got it back I put it back in my setup with all 7 USB ports in use:

 

USB floppy drive

M-Audio M-Box II

iPod connector

USB KVM switch

external CD-RW drive

USB speakers

USB camera connector

 

It was okay for about 1 day and then the yellow light was flickering again and the PC was apparently dead.  I went over it with a friend.  We couldn't even get the Dell diagnostics to run because it was constantly restarting!  We pulled all the memory and tested it in another PC; each stick tested 100% okay.  Anyway, we put the memory back in, left it overnight, and to our disbelief, it started perfectly the next day and ran over night without a hitch.  And it ran flawlessly for 3 months without any further problems.

 

Cut to this morning when I came in to see that it had restarted.  I was hoping Microsoft had issued a security fix (on a weekend?) but no, it was back to its old tricks again.  It's now sitting on the floor with the side off.  I tried reseating the memory hoping that it would make a difference but no.  The only thing that I have done recently is to download a lot of work stuff and burn a couple of CDs.  I also removed, replaced various other power cables; SATA, PSU -> mobo, etc. but nothing makes a difference.  At this point I don't think it will restart at all and it cuts straight to the flashing yellow power light.

 

My best theory at the moment is that having all seven USB ports in use was not good for the PSU (I think it's a 200 or 250 Watt PSU - not sure) and that it has bitten the dust as its predecessor did.  While trying to get it working I did get an error that the boot sequence had quit at the [WRIT] point, but I'm wondering if that was just the point where the PSU gave out.  I was messing with the memory at that point and also got the two beeps and the 'memory configuration has changed' message.

 

So, to anyone who might care to assist.  Do I replace the PSU with something like the Antec True Power Trio TP3-430 ATX12V 430W PSU, or is something else going on here?