Not so sure Tanev is worth that, his contract is expiring, he has apparently been playing hurt(mentioned on the broadcast briefly) and also has a bit of a history with missing time.
I know you can't let history of injury hold you back, but Nolan, Foligno and a few other head shaking trades should be enough to give you pause. Including solid young talent in trades, players that will be on affordable contracts going forward, is a game where the cost almost never covers the benefits.
Let's just say you overpay for a player like Tanev, he plays all the games and gives you good service, but not a cup. The question becomes can you afford to re-up an aging guy who's going to want more money than you can or should spend. In the end in that case what do you end up with?
You can't win'em all, but if you want to win it all, then you absolutely have to win the high cost trades by either bringing a cup home or by having a really solid leader in the dressing room for a few years.