box enclosure 600 1 4 ohm

I need to take measuremets but 16x16 and however tall sHould be ok in my space. i would love to find a nice quality downfiring 12" enclosure. let me know what you have. ALSO LOOKING FOR 600RMS AT 4 OR 1 OHM( thanks for any help, show me anything if you think tehre is some possability that i...