Well another happy x-fire owner with cleaner front speaker output and better sub-woofer bass.
Because less bass is going to the front lower speakers you are able to increase bass level and volume which in turn drives the sub-woofer more. For us the balance is just right now where previously the fronts would start to distort or sound muddy and little could be heard from the sub-woofers.
We fitted 330uF 35V capacitors which we got via Amazon
Thanks to everyone who added to this thread, was a quick and easy job, in fact it to longer to read this thread than it took to fit them!
We decided to use spade connectors so that we could remove if we didn't like what we heard, wasn't necessary.