Mark Levinson set up Cello about 20 years ago after he was forced out of his own company (alledgedly). He left Cello about six years ago. The kit was stratospherically priced and to be honest, the stuff I heard many moons ago seemed good, but not outstanding.
Possible exceptions were the Stradivari Master loudspeakers, built using top spec Dynaudio drive units. Awesome scale and dynamics. Some of the Cello loudspeakers are excellent value now used, but the Palette still costs a fortune (despite it being overhauled by modern EQ's), and the amps seem hard to justify these days performance wise. It really was a case I am told of needing a full Cello system to gain most of the benefits. Even today, that's still a scary prospect.