What's the best way to keep our great BoD after we go public? I'm concerned Sox is going to scare them off.

A few things you can do:
-Know that it's coming. Ask your board before and during the IPO process what their intention is post-IPO. You can't fight it until you know what the problem is. Once you know who might bail, discover and work on their issues one-by-one.
-Load up on D&O insurance
-Have world-class auditors and corporate counsel
-Have enough talent on the board that you don't overload members with committee responsibilities
-Make it worth their while in terms of compensation and in terms of networking. That is, if your board has great people on it, board members will tend to stay just to have those valuable connections
-Make your numbers. A successful company is a feather in the cap of the board. A failing company is a sinking ship.
-Co-opt other board members to help keep them on-board. If you have a notable board member with a good relationship, they may be able to help out here.

Things you can't do:
-Some investors/board members have a simple policy: no public boards. Can't get around that. But you should ask your board now, prior to going public, where they will stand on that subject.