I have a biocube and the ballasts are OK so far....
You can totally run the system WITHOUT any modification....All I did was to add a bag with carbon to compartment #2 and thatz it...
Of course you could make a refugium in compartment 2 with live rock which would be better than bioballs - but bioballs do work if you do the proper water changes and monitor the amounts of food that you give to your fish.
AND - biocubes look very slick and nice! ex.
http://picasaweb.google.ca/edikpok/29gBiocube#
Also - check craigslist if you have it in Edmonton. Sometimes you can find cheap biocubes ()$300) there