If you are going with ARC, you will need to move up to the REF 3 to supercede what you already own. If you are not hearing the differences between a CP-700 and something lesser in the ARC line, then there is something wrong with the synergy of the system (speakers, sources, cables, etc). The only ARC preamp that would give your Classe a run for its money, would be the ARC REF 3 preamp, and that would not be by much. In my opinion, definitely not a $3500 difference.
I know all of this equipment well, and would regret to see anyone make a mistake in an expensive upgrade option, even if they had money to burn. In my opinion, there is not a manufacturer that gives your CP-700 a run for its money other than the Einstein. Sometimes it takes a signficant financial investment to receive a true upgrade in system. Otherwise, it appears a unilateral move is being made.