I think "Vertical's Currency" is the best of the Hanrahan stuff, too. A good place to start with this work, anyway.
"Harmony Row" is probably my favorite of his solo albums, but "Songs for a Tailor", "Out of the Storm" and even "How's Tricks" are pretty solid recordings. There's also a pretty good compilation called "Willpower" that's got a good cross-section of tunes.
BTW, most of his early solo albums have been remastered and re-released in England with extra tracks. So, it's definitely worth tracking those down.
One more thing - I recently grabbed a 2-CD album called "The Jack Bruce Band Live '75" which is EXCELLENT. A lot of music from "Harmony Row" and a killer band of Mick Taylor (former Stone), Carla Bley, Bruce Gary ('future' Knack drummer) and Ronny Leahy (on keyboards). Check it out!