Help me out with this riddle

Can you post the entire riddle so that we can get some context?

Oh, and welcome to A2K!

Could be Dennis Hopper but need the entire clue.

Ok, the whole riddle is:

'What links the following (and, if you can be bothered to explain, why)?

1. Voltaire in a brothel
2. Steve Rogers
3. Collecting Basquiat, Haring, Scharf...he could be a space...
4. Jack Napier
5. If Six Was Nine
6. The "Wall of Sound"'

Now, the Voltaire-brothel connection is probably something about the story that he was encouraged to visit said establishment by some friends and went along. The next night they asked him again and he refused, saying "Once a philosopher, twice a pervert" (in some versions it's a gay brothel, and the quote is "...twice a sodomite").

Steve Rogers is the alter-ego of Captain America (or, less likely, a pitcher who used to play for the Montreal Expos).

I'm liking Dennis Hopper for the third clue - I take it he collects the work of these artists.

Jack Napier is the guy who becomes the Joker in Batman (or, much less likely, a male porn-star ).

If Six Was Nine is a song by Jimi Hendrix in which he gives the finger to white, middle-class America for looking down on his non-conformity: "I got the whole world to look through / And I ain't gonna copy YOU."

The "Wall Of Sound" was a studio set-up invented by legendary rock'n'roll producer Phil Spector.

That's as far as I've got.

Hmmm the only thing I'm getting is Voltaire in a brothel could also be a reference to Dr. Pangloss (in Voltaire's {i]Candide[/i]) saying "This is the best of all possible worlds."

Eek, the rest of it is a total stumper.

Ok, I know the answer now. Not that I really worked it out; more like I gave up and asked for hints.

The link is the film 'Easy Rider', starring Jack Nicholson (ie The Joker, ie Jack Napier) and Dennis 'I collect paintings and am a space-' Hopper. If Six Was Nine is on the soundtrack, Phil Spector has a cameo, one of the characters is nicknamed Captain America and I can't remember the Voltaire connection, but perhaps if you've seen the film you'll be able to work it out.

Thanks for the help anyway.