The Chicago Chamber Orchestra is one of those low-profile local groups that offer programs mostly for free and that are taken largely for granted. Under the direction of its founder, the redoubtable Dieter Kober, the 35-member ensemble gathered a cult following as an inexpensive introducer of beloved classical works, and its quality was wildly uneven, though good performances outweighed poor ones. Now Kober has retired, and the orchestra is looking for a new leader. In the meantime it’s been performing with guest maestros, sometimes with unexpectedly exciting results. The guest at this concert is Douglas Bostock, one of the outstanding British conductors of the under-40 generation. Bostock is steadily building a reputation in an unlikely part of Europe: he heads the Karlovy Vary Symphony Orchestra in the Czech Republic and the Chamber Philharmonic of Bohemia; by now he should be steeped in the Central European way of playing that so impressed composers from Mozart to Dvorak. Aptly enough, Dvorak’s folksy Czech Suite and Mozart’s Haffner Symphony headline Bostock’s debut with the CCO. Also included is Albert Roussel’s elegant yet peppy Concerto for Small Orchestra” a seldom-performed work. Sunday, 3 PM, Preston Bradley Hall, Chicago Cultural Center, 78 E. Washington; 346-3278.