[Leica] Manual flash or SF20 or SF24 for M6TTT

[scott at adrenaline.com (Scott McLoughlin)]

Kind folk,

I'm shopping for a capable flash unit for my M6 TTT. By way of 
background, I use a Nikon SB800 with my D70, FM3a and g'friends N80. It 
works really well. Powerful, tilt, built-in bounce card and diffuser, 
TTL support of various flavors, powerful enough to leave a diffuser on 
her and shoot away.  It's kinda big, but I love the wya she just works.

For my M6, I have the little Oly S20. It's small and simple. I got the 
Kaiser PC to hotshoe adapter for a little flexibility. But she only has 
a few auto modes, isn't all that powerful. I don't see how to figure out 
the settings to accomplish bounce, although I've heard kleenex can make 
a good diffuser. Anyway, it's a keeper because its so darn small.  I get 
mixed results out of her.

So now my queston. What can I get for my M6 that's more like my nicely 
cabable and well appointed SB800. Ease of bounce, plenty of power, some 
way to setup for outdoor fill flash.

Does this have to be a Leica flash unit (no bounce without the SC-17,  
right? But I already have one of those).

Or will a Vivtar do the trick? I don't have alot of experience with 
non-dedicated flash units. What about Metz? Some of their units look pricey.

Any help appreciated.

Scott