It would be huge to land either one of them, but as you said, the cost is probably going to be steep. I'd imagine both those teams are going to try and gouge you since you are going up against them in the playoffs. Ovi is amazingly worth as much as Stamkos with your league's settings (261.8 pts vs 259.4 pts by my count), due to 1 pt for peripherals. If you are going to go after one of them, Ovi seems like he'd be a much more affordable option and will provide equal value with your scoring.
1 yr league, 10 teams, H2H points: G(3), A(2), PPP(1), SHP (2), SOG (0.2), Hits (0.2), BKS (0.2), W(5), SV(0.2), GA(-1), SO(5)
Roster set daily: 10 F, 6 D, 1 Util, 2 G, 3 BE, 1 IR
Forwards: Tavares, Ovechkin, Ribeiro, Parise, Benn, E. Kane, Skinner, Brown, Backes, Steen, Tarasenko, Landeskog, O'Reilly, Saad
Defense: Letang, Phaneuf, OEL, Streit, Carlson
Goalies: Price, Rask, Kiprusoff, Emery