As investments go, fine art and precious metals are nice. But Craig Kallman prefers vinyl.

Crammed into 14 rooms at a climate-controlled Manhattan warehouse where auctioneers including Sotheby's store art, and in the Upper East Side apartment he shares with his wife, Isabel, and their 10-year-old son, Mr. Kallman has about 750,000 records, 100,000 compact discs, and 1,000 rock T-shirts (alphabetized, so he can find AC/DC or ZZ Top quickly). Not to mention a smattering of Beatles lunchboxes, Blondie store displays and KISS...