The report about the Su-30s was from Dubka, and that is a very unreliable source. The report I just posted up is from Defense Update, and they are much more reliable.
If the Iranians want to completely protect all their nuclear assets from an Israeli air attack, they're definitely going to need a lot of S-300s as a nuclear program (even a peaceful one) requires many facilities. The Iranians bought I think 24 Tor-M1 batteries last year so about two or three dozen batteries of S-300 would be good compensation, plus don't assume the Iranians can't afford it. They have one of the largest oil and natural gas reserves in the world, and much of their spending goes towards domestic defense purchases and R&D.
Well I guess that depends on your definition of "dozens". Hearing that made me think of around 75 batteries which would be a little much, to say the least. However 24-30 is a much more believable number. It just isn't clear enough.
I guess will just have to wait a little bit to see whether the batteries are delivered or not. My guess is that they will be. The offical denial is probably just there to confuse the US while the sale is completed.