HIS will take a month with 3 weeks if it sitting in the RMA warehouse if the card dies under warranty.
XFX has a faster RMA turnaround but not great.

Do go voltage unlocked and consider the warranty..  If the card dies, the warranty is what will matter.
Google bitcoin mining comparison and read the wiki.  If it is a fast BTC card its usually a fast altcoin card but you need to search 1st.