Ghost, obviously having a gauge around is good for peace of mind, to know when to get off the throttle, although if you plan on tuning/attempting to tune the car yourself or just don't like having to pay for dyno time, I would recommend going with a wideband that you can datalog with.
I'm not sure what flavor of eManage you're running, but if you're running EMU, and it supports a LC-1 or other wideband that can allow you to datalog through it, that's what I would go with. I've played with cars with UTEC's/DTEC's w/widebands, so I'm a little partial to having the ability to datalog your AFR's, so you can make specific adjustments at the needed RPM points.
If you're just going to have the car dyno tuned with a tailpipe WBO2, and don't plan on playing with anything yourself, go ahead and get a gauge, that is if you aren't interested in data logging. Me personally, I prefer a digital display as opposed to gauge, like the ones TurboXS uses:
http://www.turboxs.com/more_info.php?ID=179