have woofers what do you experts recommend

[nunayafb]

Ok, just got into this diy speaker thing, got SW all calibrated and everything did some impedance measurements on some 12" Technics woofers. Th eseI would like to possibly use in an isobaric configuration or my rockford fosgate 12"DVC with all of the bells and whistle that a sub should have.
My question is what are the problems with using car woofers in a large room, would the right box and possibly a LT sound good, or will the massive resin impregnated paper chunk cone be two heavy for transients.
The flip side involves 2 12's in the clamshell design and the light cones although flimsy are effectively doubled in strength by the isobaric config. so I have heard. I have already bolted the two to the ported 1/2" mdf box that was designed for each on and this configuration really cleaned up the bass.
Problems, the 12's have a slightly high Fs, ~33hz (estimated) and I dont know how deep they will play as a result also really small magnets, and of course small voice coils the RF12 being the opposite.
Also when measuring and testing the isobaric configuration do the two need to be bolt together at all times for all tests.

wow I must be tired, the above is somewhat incoherent, so much for college.