Serious Six finished the end of August for me at 42N.
Bangi Haze finished the end of September. Yields well, no PM, mold resistant.
Mandala #1 was my best all around strain, finishing about mid-September. It's been discontinued and replaced by Fast and Glorious, which I have not grown out yet.
Purple Paro Valley is an excellent strain for Northern Growers like yourself. It will finish about the third week of September. Very relaxing and lightly euphoric.