Hmm...well, what do you like...what do you want to play?
Primarly TBS and the occasional RPG. I hate RTS with a passion bordering on irrationality, so while Knights of Honor has some good mentions here, I know I'd hate it.
I played Dominions 2, but I might check out 3. Played GalCiv I&2 and Space rangers. Good stuff. Sadly, I've already played Armegeddon Empires and now I'm looking forward to Vic's next game later this year. Played a lot of Blood Bowl, probably 60-70 games and finally got sick of beating up on the crippled AI
Maybe I'll go back and break out one of those previous ones for a while. I never did finish Space Rangers 2.
Hmm, well, Im really enjoying Kings Bounty:The Legend. It's a turn based (in the battles on a Hex grid) tactical RPG with an appealing presentation, and a sort of quirky addictive charm. You might enjoy giving that a look in the Impulse store.
As for SR2, the impulse store now has an expansion for it ("Reboot") that I'm told significantly enhances the original game, if you were going to return to that.
As far as "Turn based " strategy, there havent been any really good entries in that genre for a while that I can think of, assuming you've played all the classics. The most notable one I can think of recently was Empire Total War (Turn based on the Campaign Map, not the battles), and that game has reportedly seen patches to a number of issues that hampered it at release, if you were of a mind to check that out.
The most notable ones in the "spirit" of TBS games current now (Like EU3 and next week's HOI3) use that "continuous turn based" model that unfold in real time, but arent RTS. (You can pause and issue orders at any time, then start time moving again, so you get to plan strategy at your own pace, like any TBS game)