personally?

Party
Dise
Pokerroom/I-poker

To be honest if you can play 25nl you probably want to be on party if you arent chasing bonuses.
If your playing <25nl then i think perhaps boss media or maybe prima offer good fairly low variance games. Add dise to that at 10nl too.

As far as i know, I-Poker has some very good higher limit games as does dise.