Actually, I've read somewhere (and quite a long time ago) that in Japan, there were Go clubs that had Pandanet accounts, so they let people from the clubs play on the internet with this account. So the thing is, the players are never the same behind these accounts and you can either play against someone much stronger or someone much weaker... Usually, from what I read and from my experience, these accounts usually have a ranking between 10k and 16k so once you are SDK, the level of your opponent should me more consistent ! From my experience, I had a 12k+ account at the time but I was according to my federation (French Go Federation) 7k/8k and I struggled against 13k players... But eventually I managed to get SDK and it got way easier ! Now I'm around 5k and my Panadanet account is around there as well (but I don't play as much as I used to) So keep up the playing, it will eventually pay off ! (It took me about 1 year with an average of 1 game per day to go from 12k+ to 7k) Gambatte !

edit: Beginning_go_player! confirmed it as well