If you're a high roller, there's still probably no singular book that's good for you. For example, BetKing takes 2 BTC bets on some soccer events no problem, but they won't let me place 0.07 BTC on an NFL outcome. If you care about limits for all sports, Nitrogen is likely your best bet.
We have had some of the highest limits for a while now, for example we were offering 100 BTC limits during the world cup!
Obviously it varies based on the sport, specific line, the time left till the event, etc, but for most main markets I like to think we are up there with the asian bookmakers and Pinnacle.
Ronnie @ Cloudbet