I use a 30 gl to house my recirc skimmer with extra LR and no direct lighting as well as a 55 gl divided into 3 chambers(DSB-fuge/plenum-fuge/and return for a submersible 900 gph pump). Although my display is only a 55 gl, I have added about 80 more potential gallons to the system and know first hand that I have a much more stable water quality.
There's nowhere else I'ld rather be... unless, of course, you're buying