I used to own a pair of SM-70's. Here are my suggestions:
1. Even if you only have one now, get a pre that's fully balanced (not just blanced outputs) They sound so much better as balanced mono's that you might as well plan on running them that way.
2. I liked the sound I got with an Electrocompaniet EC 4.6. It's fully balanced, has a remote and looks decent enough. Along with that it sounds great in the midrange and smooth in the highs.
3. Silver IC's worked well. I used Homegrown Audio Silver Lace XLR with nice results. Didn't really get to try anything else.
Have fun with them! They are great sounding amps with the right component matching.