I have two rigs with:

3 x XFX 7950 each. Doing about 550kh/s per card. Sometimes on new coin launches, when diff is still low, I also setup some DigitalOcean droplets to mine at the start.

For a tutorial on that: http://dogecoin.ga/dogecoin_mining_cloud_servers.htm

Doing this about 1 month now.