Which 28-105?

[Robert Gonzalez]

I was just browsing B&H's site pricing the popular Pentax 28-105 zoom. 
But wait, there's three of them:

Price: $ 199.95
Zoom Wide Angle SMCP-FA 28-105mm f/3.2-4.5 AL IF Autofocus Lens
Price: $ 357.00
Zoom Wide Angle SMCP-FA 28-105mm f/4-5.6 Autofocus Lens
Price: $ 189.95
Silver Zoom Wide Angle-Telephoto SMCP-FA 28-105mm f/4-5.6 IF Autofocus
What is the difference in quality between these three?  I'm confuscated 
now....

rg