There is a reason that Klipsch work so well with Tube amplifiers, because tube amplifiers can drive virtually any load. Most Klipsch speakers are very efficient, more on average than any other manufacturer, but they can be very taxing on amplifiers because of their tendacy to fluctuate in impedance. Once the amplifier loses control of the speakers they can sound aweful. I recommend putting something behind the Klipsch that is at least 4 ohm rated, regardless of what Klipsch specifies the nominal impedance to be, more often than not they will dip lower or higher than that on a regular basis.
A budget Behringer would work, like the A-500. You might also look on Ebay for older home/pro audio amplifiers from Carver, Hafler, many others the list goes on and on.