The Powerhouse actually consisted of Stevie Winwood on vocals, Jack Bruce on bass, Paul Jones on harmonica, Ben Palmer on piano, and Pete York on drums. At the time, Winwood and York were part of the Spencer Davis Group, and Bruce and Jones were in Manfred Mann. Palmer, by far the most obscure member, had been in a band with Clapton during a brief time in 1965 when the guitarist had left the Bluesbreakers; later, he'd be a roadie for Cream. Of course, Clapton and Bruce would soon team up to form two-thirds of Cream, and Clapton and Winwood would play together at the end of the 1960s in Blind Faith. In addition, Cream did two of the songs from the Powerhouse session, Crossroads and Steppin' Out, in concert. The Powerhouse versions of these songs were inferior to Cream's (and, in Steppin' Out's case, also inferior to the version Clapton had done with Mayall), containing less energy, and differing from the more famous renditions by including piano in the arrangement. I Want to Know was just an average blues-rock tune, credited to "MacLeod," which was possibly a pseudonym for the group or for Paul Jones, as Jones was married to British author Sheila MacLeod.
As interesting footnotes, Winwood was credited under the pseudonym of either Steve Anglo or Stevie D'Angelo on the original LP, probably to avoid contractual problems. However, Clapton admitted later that year in the British rock press that "Steve Anglo" was in fact Stevie Winwood, though it didn't stop Winwood from using the "Steve Anglo" pseudonym again for a recording with John Mayall, Long Night, soon afterward. Also, for all its obscurity, I Want to Know was covered by Ten Years After on their first album in late 1967.
The session itself was done in March 1966, at the instigation of Joe Boyd, who had just gone to London to open a U.K. office for the Elektra label. Paul Jones suggested getting together an all-star band and helped Boyd put together a proposed lineup. That lineup was the same as the one that played on the What's Shakin' tracks, except that the intended drummer was Ginger Baker; as Baker was away on tour, Pete York was used instead. Clapton, Winwood, Baker, and Bruce were still pretty unknown in the U.S. when the LP was issued in 1966, and even many big fans of Cream, Traffic, and the various musicians involved remain unaware of this early collaboration. In a March 1968 interview, incidentally, Eric Clapton said that an unreleased fourth track, a slow blues, was also recorded with the Powerhouse, although it has yet to officially surface. ~ Richie Unterberger, Rovi