Sort:  

Siacoin can be mined with a Obelisk miner or a Antminer A3 . For the moment those are the best choices on the market. A mining rig that runs on GPUs will cost a lot more than a Antminer A3 for example.
This is because Nvidia raised their prices on good gpu and to have any returns you will have to wait a long time. So a antminer can be a good choice.

yes mining on GPU consume a lot of electricity beside initial investment on GPU. Thanks for sharing @cynetyc