Not sure about any 'ultimate' but after a couple of months with my rt12d, I am extremely happy with this sub. Hell, this thing can be felt outside when I have it cranked up. Putting two of these into any room would require some serious space. Maybe you are some punk *** kid with a single room that your father lets you live in where you have the means to afford the volumous space needed for two 12ds. I am yet a humble working man living in a simple split level and one 12d is more (and my mother would say way more) than enough to shake the foundation. Everyone that has been in the house to exeperience the power of this sub has been awed. On top of that the Klipsh sound has blown them away from anything that they have ever heard or experienced in similar environment. Suffice it to say that horns do have a special sound and the 12d does fit in with the whole of the experience. From my personal experience of setting up my AV is that the room has a huge impact on the expected sound. I had no idea that it would take so much power on the bottom end to compliment the brightness of the rest of the system. I started with a KSW12 that came with the set of speakers that I purchased and it simply did not have the impact I wanted for my AV. The RT12d has been phenomenal as a replacement to that sub. This is not to say that the KSW12 is a bad sub.. Is was just not right for my living room. The plan is to use it in my bedroom. Sorry Klipsch but there will be a YSP4000 goiing with that sub. HINT HINT please look into a (horn loaded) speaker bar that can be mounted under an LCD [with HDMI]. Your 2 cents have thus been refunded and scratch tickets returned in their place. It is so extremely appearent that you have yet to hear the subs in any 'real' home accoustic setting that it may also be possible that the RF-83s are in need of some serious tending for sub support.
Without a doubt, the RT12D is an awesome piece of machinery that warrants serious consideration for those with a need and a means.
My RT12d sits very proudly in the corner of the room, oh so exposed and oh so loud!
$1400.... (Money talks!) ($.02 walks)