Well don't listen to me for a review- hopefully some members can give their feedback, I've not met anyone who was dissapointed! Mind you they don't turn it into a Lotus Elise...
However, the Stage 2 retains the ARB, so means that you don't have to compensate with a stiffer spring (no problem for a track car on coilovers) which is more suited to road spec spring rates.
Stage 2 and Stage 3 are really for different purposes, stage 3 allow castor adjustment, and is heavier gauge material to compensate for the compression struts and loading directly on the frame. The struts are the main cost increase (and some more labour/fab time) the frame design is common between Stage 2 and Stage 3.
You will need ARB blocks (which PPP sell for £60 delivered) I would reccomend getting the TCA bushes in nylon too (PPP sell for £45 delivered) as the Poly ones tear- I've tried 3 different brands and they're all poor.
Driving a car with ARB Blocks, TCA Bushes and a Stage 2 Frame fitted, and then driving one without, is like night and day, I gave Sam the keys back to his G40 after one lap round the track, I didn't have any confidence in the car but I'm used to driving Polos that are solid and twitchy!
Here's me fitting a stage 2 to my daily driver:
http://www.polog40.co.uk/forum/index.php/topic,9016.15.htmlI could bang on for pages about them, if you've got specific questions fire away, I'll do my best.
Cheers
Pete