Imac kernel crashes

I have owned an Imac for 2 years now and since the day i bought it i've had multiple kernel panic crashes. Mac forum experts have suspected third party software: Logic, PACE, Apogee maestro, East west play, etc.
About 8 months ago i erase installed Leopard and re-installed all my software 56 hours and had a couple of days problem free.
The crashes returned, burned out Ensembles in/out puts and finally Ensemble would not power up.
A new Ensemble arrived and started shutting down on it's own whilst in use by firewire, and would not start up in stand alone. I finally got it to work.
2 days ago i had 12 crashes in 4 hrs. so i decided to erase install Leopard and re upgrade to Snow Leopard v 10.6.8 and update it.
As a test i did not install any programs, all apps are from the OSX install disc.
It crashed whilst watching a tutorial in Macpro video and again whilst navigating to Icloud info.
and finally a kernel crash while i was in systems preference checking voices in Speech. I had to re-satrt using the power button.
Question:
Am i right in assuming that Imac has a hardware fault?
If so i can have it repaired under guarantee.
If Not i will end up with a considerable bill and a Machine that wont even work with the basic installed programs.

For 2 yearsI have done all the possible test and fault finding routines that are available and not been able to resolve this issue neither have any forum experts been able to pin point the trouble.
MacBookPro has the same OSX and 3rd party apps and not had a single crash in 2 1/2 years
Unfortunately it does not have the capacity to run Logic and all the plugins i need in my production.

It sounds like you have done thorough testing, and you have come to the right conclusion. It sounds like it is possibly a hardware fault.

If you have done a fresh install of the operating system, and have not added any other applications and it still has the kernel panics, then it is most likely a hardware error.

Your best bet would be to take into an Apple store so that they can run hardware diagnostics tests on the unit to see which part is causing the problem. Do you have an extended warranty on the unit? Or else you may need to pay for the repair.

Another thing you can try. Do you have a firewire cable? If so connect your Macbook Pro to the iMac via the firewire cable. First power up the Macbook Pro and hold down the T key (this will boot the Macbook pro up in Target mode.)

Then boot up you iMac whilst holding down the Alt key. This will bring up any bootable options. Wait for your Macbook Pro to appear, then click it to boot up into your Macbook Pro's operating system.

So now you will be running your Macbook Pro operating system via your iMac. This is a good way to test if it is the iMac hardware. If you still have kernel panics then it is definitely a hardware error on the iMac. If you don't then it could be some software error on the iMac.

If you have a local Apple Store, or local Apple Authorized Service center, you can have them troubleshoot it for free. They can tell you if any hardware is bad, and what exactly is bad.

If it's under warranty, it'll be repaired free. If not, it will be a flat $350 repair fee (Apple Store) no matter what's wrong. You get back a working Mac.

Could be bad RAM, bad data bus, bad GPU, so much could do these things. I'd have a shot troubleshoot it and repair it.

FYI, my 2008 17" MBP died last month. Apple Store found bad GPU, bad hard drive, and replaced both for the flat $350. I've had this done a few years ago before we had a local Apple Store, and the system board alone (GPU is on the system board, meaning the whole board gets replaced) cost $600, plus the service fee to actually replace it. I consider it a good deal.

When you install the OS (which I don't think is necessary), be sure you install the latest drivers for your external hardware, and make sure that hardware has it's firmware up do date.

Great advice BenB, thanks for the informative reply.