Hey Patuba,
I have done several cycles of SU now, and I've done no cardio on one and 4 days/week on another. Cardio isn;t entirely necessary while on SU, but it's always a best bet, no matter what cutting cycle you choose. When I did 4 days, 2 were 45 minutes lower intensity and 2 were 20 minute high intensity. I had great results, although SU works on a completely different mechanism, so you aren't exactly enhancing it's effects, but do your cardio anyway.
Now SU make most lethargic (especially in summer), so you may have no desire to do cardio, but pop some ECA's and you'll be ok. When I didn't do any cardio I still got great results, about 2 lbs difference. With cardio on a 2 week cycle I lost about 9-10 lbs, without about 7-9 lbs. Hope this helps.