which c-j amp

I'm currently using a c-j PF-2L into a c-j MF 80 all plugged into an Adcom ACE 515 power condtioner into Thiel CS 2's all wired with Straightwire LSI Encore. Some say that the MF 80 is one of c-j's better amps as it only has one transistor per side and therfore there is no issue about matching and smearing, but I've recently moved into a bigger room and am considering more power. I am also considering moving on to Thiels with a more demanding impedance load, from 6nominal/5 minimum to 4nominal/4minimum. My hopes are to improve the bass response of my system which can be a bit bloated on occasion, I do realize that the problem might be elsewhere. Has any one compared the older c-j 2300 (240 watts per channel and supposedly better output into lower impedances) which is all MOSFET to the newer 2250 (125 watts per channel) which is MOSFET and BIPOLAR (supposedly better for bass response). They both seem to be going for about the same price ($1000) on the used market. Any other ideas at this price point would be welcome. As always thanks in advance.