Hands down, the cheapest I've seen the Proline suspension kit ($48) is HERE:
http://www.southsidehobbys.com/Prolinepg6.html
That's
$20 less than Tower Hobbies!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I didn't even know Proline made this till a few days ago. I like it 'cause you get new shock towers, turnbuckles & hinge pins too, not just the arms.
But it's created a minor dilemma, as I was pretty much set on the RPM stuff. Lifetime warranty, nice color choices & lots of customer testimonials for RPM, but Proline makes quality stuff & you get an AWFUL lot of stuff for $50 in this kit.