I've just crossed that bridge myself, I'm after steem power ATM but onsite takes 3 days, and who knows what the market price is then. So I go to Bittrex try to hold out for a bit better btc price, and do the same BTC to steem. Or just do the best bid and then offer, bing bang and power up time :-).
Only small amounts so far 6 - 10 sbd, I'll try to get more sophisticated when its more.