SUSPENSION KITS (SPORT)
APEX
AVO
BILSTEIN
PI
SPAX
H R

+lowering kits

which 1 would be best though

I have -60 mm all round on my car using PI springs and shocks.

Although the handling is great, and I can go round round abouts really fast, Don't waste your money buying and fitting these as they tend to fail the MOT for being 'coil bound'

I ve got to buy some new 1s for my cally but i cant remember which one there was on it the last time i changed them

H & R are probably the best, but they're v. expensive.  I believe that it was what Frank used on 'The Beast' - probably the best Calibra in the world [until it was sold for the bits].
Next, I believe are Bilstein struts with Eibach springs [lowered if you want], but I don't know how they compare with the Apex.
You can slam a Calibra as much as you like - the most I've heard of was 110mm!  But, if you slam it that much, you need to modify the wheel arches.  Also if you slam it much more than 40mm you start needing compensation kits to correct the camber, otherwise you'll get bad tyre wear.  30-40mm is probably the best compromise.

Here's a side on picture, its actually a lot lower than it looks, as the underside is actually lower than the side sills.

Bear in mind that my car has no side skirts or any other of the plastic mud traps fitted to it.  With the side skirts fitted, it'll ground out on every hump as will the front bumper with them stupid splitters.

I'll try and get a clear on day light picture tomorrow as that one is well old and the car looks a little different now.  I'll also take a photo of the coil bound problem.