I prefer the strategy of matching amp to speakers rather than going least common denominator, but if you must have speakers that will match to the widest variety of amps, I'd say horns (high efficiency) or something efficient and with > 8 ohm impedance (not very common) for improved damping factor with most amps. I think Harbeths mentioned may fall into this category, but not sure. Rogers I'm pretty sure does.
If you match the amp properly using something that is high current and doubles output from 8 to 4 ohms, like many Class D amps or some Musical Fidelity's I'm familiar with for example, I'd say Ohm Walsh series 3 is the best moderate cost floor standing full range I've heard. Depending on room size they range from $1000-$6000.
If the sky is the limit regarding budget, then you have many fine choices if you match components carefully depending on taste and preference. Good monitors with limited low end will cost less, good full range floor standers will cost a lot more.