Thanks for the responses. I have somehow expected the answers. I need to justify the cost of adding another sub as two subs would cost more than the main speaker itself. That will come later. I'm currently using one sub with a bookshelf speaker with great success. Integration was pretty much seamless. Going to consider some higher quality monitors and add another sub later when opportunity beckons. Need to figure out how to add another sub into the system though as the preamp has run out of inputs.
Cheers.
Cheers.