General guidance is with either the 150 or the 180, an 8mm or 16mm extension tube. It's enough to bump up the close focus without altering exposure significantly (you're talking 1/4 or 1/3 stop compensation, which your aperture/shutter combination isn't capable of anyway). If you think in terms of 35mm lenses, the difference between the 150 and 180 focal-length wise is the difference between an 85 and a 100. Frankly, I'd go for the 180 if you have to choose.