Greg, the first point is that the 240 rating is 65 watts, using the more realistic two channels driven standard. Then, as Randy mentioned, HK is also conservative and takes their rating farther down on the distortion curve than they'd have to; the rating would probably be about 70-75 watts on the same standard which the 2106 uses for a 100 watt rating(which is an accurate rating, as legally required by the FTC, and is 20-20KHz, full range). That number of watts should be enough in most cases, and if it wasn't, 100 watts is only about 1-1/2 dB more in maximum output and wouldn't make that significant of an increase in capability.
It depends how good that price you mentioned is. The 240 is available for around $350; the 2106 for around $500(the HK 435 is also around $500 and so is more nearly comparable in price). My own view would be to go with the 435 or 2106 if the budget will stretch a bit.
