evaluating ressources saving between differents families

One (obvious) method could be to make some test designs in Quartus and compare. If you know quartus, its simple and its easy to swicth target. If you dont have Quartus you can download web edition for free, but you will of course have to spend time learning to use it!

Just had a quick look in megawizard and that says

Resource result is for 8x8 mult

Cyclone: 117Lut's

Cyclone II, III: 1 Dsp-9bit block

Stratix " ", II, III: 1 Dsp-9bit block

Resource result is for 16x16 mult

Cyclone: 357Lut's

Cyclone II, III: 2 Dsp-9bit block

Stratix " ", II, III: 2 Dsp-9bit block

Resource result is for 32x32 mult

Cyclone: 1221Lut's

Cyclone II, III: 8 Dsp-9bit block+110Lut's

Stratix " ", II, III: 8 Dsp-9bit block