Yeah that's not a good roi. Underclock and under volt a set of 6 used r9 290x. Mem clock to 1160 and you'll be at aboit 1100w. Mine eth and lbry. Sell your coin and buy zcash if in the end you want zcash. You'll spend about 2100 on the cards. Profit should be about 400 a month, double what you have priced. Take that extra cash and buy a steak every week while you sit back and smile at you acct value
I am not a fan of the topic starter's idea of building such a rig, but buying 3+ years old that have been mining at 300W and 90 degrees C is not any better.
Not to mention that lbry now belongs to asic's territory, you won't make more than 10 cents per card per day - dual mining is not that worth it anymore.