As I understand it, the most important thing to look out for as far as speakers mating to particular amplifiers is that the amplifier has enough power (usually expressed as watts rms into 8 ohms) to adequately drive the speakers without clipping. There are two important figures to keep an eye on with speakers - sensitivity and nominal impedence. Sensitivity essentially equates to the dB level with 1 watt of power at 1 metre. So a 96dB speaker is considered very sensitive (delivering 96dB with a 1 watt input) and would usually not require a high power amplifier. Alternatively, an 83dB speaker is extermely insensitive and would require a decent amount of power.
There is then the matter of impedence. Speakers with impedence dipping to 4 ohms or less require an amplifier than deliver adequate power and current into the low impedence. To complicate things, nominal impedence (the figure quoted by speaker manufacturers) does not indicate the minimum impedence dip, as impedence varies (often dramatically) along the frequency spectrum. So you need to ensure that your amplifier can deliver the required power and current into a low impedence load.
One other factor, particularly with some tube amplifiers is the output impedence of the amplifier. If the amp has a very high output impedence this can cause significant frequency response errors with some speakers.
So in summary - make sure the amp has adequate power, can deliver power and current well into low impedence loads (if your speakers have a dip in impedence) and check that the output impedence of the amp is not too high into a low impedence speaker.
Your best bet, IMHO, is to ask on this forum about any combinations you are considering and I'm sure you will get the answers you need. :)