It's never wasted, since for Steem Power your upvote worth is growing. So, if you convert to Steem Power, it's permanent (unless Power Down - Which takes about 3-5 steem per week). So, my best suggestion is just simply to put back from Poloniex to Steem. Convert for SBD, research a bit on boosters, and for same money earn from your own posts new SBD and new Steem Power. You can't go wrong with it.

Example:
Minnowbooster for 1SBD does around 1.95$ on your post (promoted). In payouts, you get around 0.75 SBD and 0.9 SP (SteemPower).

So practically you almost return your investment in CASH, plus you gain more Steem Power.

Cheers,

Lucifer