Don't make the mistake about adjustable. Those Konis are rebound adjustable aren't they? Koni told me the idea is that you start on soft and turn up the rebound setting as they wear.
Adjustable is the 6 or 8 way adjustable KYB or Koni sport, etc. Those might still be twin tubes and so even better I would think are the monotubes such as the better Bilsteins and the KYB ultra SR. I would call these 'proper' dampers. But they're not adjustable. Nor are they 'coil over'. I presume monotubes can be if you pay enough.
The 'coil overs' do have those nice advantages and, being thin, allow some outward offset to compensate for having lowered the car. It's easy to try different spring rates and get the height right.
I would not have wanted the front lower for road use than I had it with those springs as I NEEDED suspension travel as I drove FAST over bumpy roads. It's the main thing that annoys me with the Fiat and each time I drive over a country lane is a main motivation for changing to a car with taller wheels and proper suspension travel.
I found the Bilsteins to be several leagues better than the Spax I had as they have asymmetric damping. They remain firm at low speed giving the car control but move with high velocity impacts, ie, over bumps. Which is exactly what suspension should do and the Gaz, Leda, Avo, Spax style never did, as far as I know. Of course they may be much better now
Anyway, we can't get the better Bilstein for the 5GTT (I already asked a few years ago, well they said they MIGHT be able to supply, but maybe £500 a pair or something, so more now I'd think) or KYB (checked this week on-line) so it's a non contention. But I can get the KYB monotubes for my Fiat.
You should ask Gaz if they supply their shocks with a softer bump setting for use with a harder spring. Or the combination of the hard spring and hard bump valve might be too much. I was next going up to 300lb springs for the Konis and Koni would re valve them for those. I think Duncan Greer on here had that done with his.