They fly mainly Delta being based out of MSP, but I was thinking one of the non affiliated Amex's might be a good option and I usually see good reviews of MR points on here being transferable to many programs at a good rate. The US Bank Altitude card looked interesting with 3x points on travel (but then again, they want travel benefits and the majority of that 150k business spend isn't necessarily on travel so maybe that's not the best card). I know the Chase Sapphire usually gets rated pretty high, but I'm not sure what the high spend benefits are on that.
I confess to not knowing a ton of details on the CC game, so I'm turning to the FT community to help me out. I'm sure I've left off certain information that would be helpful for you guys to know so just let me know what else would be useful for people to make good recommendations.