TBH, i'd keep training natty for another year at least, i know your itching to do steroids but it won't be in your best interests at this time.
Building up a good base now will lead to much better gains in the long run.
It's your choice mate, but iv'e given you my opinion, i've seen it happen too often and heard the same old story " i wish i had waited a bit longer".
It's a decision only you can make, i'm just trying to give the pro's and con's.