a few years ago when I mined LTC with GPU rigs. you would get 6 or 8 MH/s from the whole rig burning 2000+ Watts.
One of the best cards at the time was the 7990 and it only did about 1.6 MH/s.
The current RX 480 does not hash more, but uses less power that prior generation cards.
GPU rigs are best hashing ASIC resistant Algos like : EtHash, Equihash, CryptoNight. SO coins like ETH, ZEC, and XMR.
The best current LTC Miner is the Antminer L3 at 250 MH/s using 400 Watts.
I have L3s for sale:
https://bitcointalk.org/index.php?topic=1802108.0