I'm sure it will turn out stout. Just keep it away from those sours of yours. 
Wow wot a concept, Sour n stout....hmmmmm. I debated putting a half ounce of corriander
in the mash, but changed me mind at the last minute...
Glad you changed your mind, that doesn't sound all that great to me. Neither does sour stout. 
I make a corriander beer that is my wife's fav of all my homebrews (mead not included). It is a marzen with an ounce of freshly cracked coriander seeds added for 10 minutes at the end of the boil after the heat has been turned off. I wrote an article about it for the ingredients special issue of Zymurgy a while back. I've tweaked the recipe a bit since then.
Interesting you should say that Tom, I was going to ask you your opinion before had a PM all set up to do the same, then backed down. As for the sour stout I do believe
there are stouts hit up with Brett that do exist commercially, tho I have not tried any.
I enjoy the flavor of Corriander in beer and the mash tun is the place to add it in IMO.
It diminishes the presence somewhat and kind of adds a flowery sweetness/aroma thing.
Anyhow, that beer had very little lag time I hope due to the fresh yeast cake I pitched
it onto and a large quantity of yeast.