OK, this is my two cents...
Proviron works as an anti-e by blocking the conversion of testosterone to estrogen. Thus, as an anti-e/anti-gyno, it is preventative in action. In addition, proviron will bind to SHBG more strongly than testosterone, leaving more free testosteron to do what you want it to do - help you grow muscle. I have never heard any reason why proviron would hinder gains.
Nolva on the other hand blocks estrogen from binding in breast tissue. Unless your estrogen levels are already such that gyno symptoms become a problem (something that proviron could act to prevent in the first place), there is no reason to use nolvadex. As far as hindering gains, there is some strong theory that nolva does just that.
In fact, nolvas effect of lowering IGF is well documented - and even thought to be one mechanism of action through which it inhibits cancer growth.
I'd stick with the proviron. At the testosterone dose you're using, it may be likely that you don't need any anti-e for gyno protection anyway. Proviron should get the job done as far as anti-gyno insurance. In addition, I believe it will likely even potentiate your gains (to what degree I couldn't say).
Nolva on the other hand in uncalled for unless your estrogen is already so high that gyno symptoms are becoming preasent. In addition, it will lower your IGF, likely inhibiting optimal gains (to what degree I couldn't say).