I'd be VERY careful with that. A lot of people play with fire when it comes to speaker ratings. Most amplifiers are rated for CLEAN power with up to 10% distortion. Guitar amps, especially modern ones, are designed to go FAR beyond that, usually peaking out at about double the rated wattage. Guitar players usually like the sound of power tube distortion. That means even with your amp switched down to 60 watts RMS, the amp is capable of pushing almost 120 watts when it is cranked up really loud. The power section gets a lot more efficient when distorion is not considered (this is why so many people say that Boogies are rated very conservatively - when in reality they just reach their ratted wattage lower on the volume control and can push further beyond that into distorion) The saving grace for most is the fact that most speakers are rated RMS as well, and they are capable of handling peaks of much higher wattage. That's peaks... not continuous playing. If all you do is play at bedroom volume, then you're probably fine, but I would never gig or play loud for any extended period of time with a 100 watt amp into a 60 watt speaker. At best you'll just ruin the speaker... at worst you'll fry the speaker and take out the output transformer in your amp and possibly more. Plugging the speaker into a lower ohm output, such as plugging an 8 ohm speaker into a 4 ohm output, will help cut down on the wattage demands for the speaker too. Your safest bet is put in a higher rated speaker or get an extension cab to divide the load and wattage up.
