IDS Sostenol 250 (original batch if you can get it) Sustevol250 (same thing as Sostenol250, but stronger), pretty much any test booster will help with strength. If you wanna get stronger though you got to train for it and eat for it. I found, for me, a great stack for strength and quality mass was:
Sostenol 250
Orastan-E
Nitrix
Novadex
That was a pretty damn good stack, gave me some awesome strength, quality muscle and awesome pumps. I am going to be doing it again, but probably with Orastan A instead and adding Vigor and Unleashed to it as well.
Good luck
Cheers!