03-12-09: PdreherThe Stereophile review and measurements of the C4 indicates (at least in the test sample) that the impedance only hit a minimum of 4 ohms and generally seemed to be running around 5-6 ohms from about 500 Hz on up.
The C4's are rated @ 4 ohms nominal / 3.3 ohms minimum / 88dB.
The Plinius SA-102 owners manual states that bridging them as monoblocks will "provide an extremely high performance option". The manual goes on to state that care should be taken when matching speakers... "the total average impedance for each chanel should in a range between 4 & 8 ohms" . So hopefully I'll be okay ???
I would read both the original Stereophile review and Wes Phillips' 2007 followup to get an idea of what the speakers are capable of and what gear he used with them to get such a compelling match.
I've found that a more involving and livelier sound can come from lowering the noise floor. I was wondering what sort of rack you're using and if you are using any aftermarket footers.
Also, I had a hunch that a quieter cable might help and I notice that Wes was using Shunyata Research speaker cables. Generally the braided designs such as Shunyata and Kimber designs are all about lowering the noise floor and keeping extraneous noise out of the cable runs while maintaining wide bandwidth and speed (which shields often compromise by raising capacitance).
You also might look at how your speakers are platformed. Might it be practical to try them on a set of Vibrapods? There is a lot of buzz that Vibrapods make excellent speaker feet for draining cabinet vibrations and resonances, and this in turn would lower the noise floor and improve microdynamics and inner detail. Unless you already have noise-lowering footers under your components, you might also try the proper weight-rated Vibrapods under each of your components, and consider making a Vibrapod sandwich under your preamp and amp.
Your Plinius as a class A s/b making about 250 wpc into 4 ohms, and in your room and with your listening tastes, this should be enough to give you plenty of volume--like peaks and crescendos up to 111-114 dB. If you're looking for more of a sense of "thereness," the key is vibration control and lowering the noise floor.