I think monkeyking has given mostly good advice here, but, I do not advise a Sampson amp, nor a amp that only outputs 65 watts per side if you are looking to power up something like the Event 20/20's (which is what I use, and I doubt you will find a finer monitor).
From my long years of working for big live sound companies I learned a few things about power amps and speakers. First, quality speaker manufactures ALWAYS underrate the power handling ability of their components. Second, power amp companies ALWAYS overrate their amps output wattage.
This is a nice thing to do it would seem to keep the average consumer from mismatching a amp/speaker combo. But a few things are missing here.
Distorting the input of
an amp can cause the amp to output up to 500% of it's listed output. So in the case of a 65 watt amp, that would be over 400 watts outputted if the input of the amp is clipped.
This is important to remember when deciding upon the power rating you need for an amp.
I run a Hafler P-3000 to my Events. The Hafler ouputs about 350 a side at 4 ohms, about 280 or so at 8 ohms. The Events are of course at 8 ohms. So while this is way over the rated power capabilities of the Events (which is really a very very very conservative rating), it also creates a whole lot of head room to keep my monitoring amp from creating distortion that could make me make bad decisions about the mix. This extra headroom also makes sure that the speaker is always performing at it's peak.
Make no mistake, low wattage amps are not good for monitoring in the studio. You are going to need an amp that at least outputs 250 watts per side at 8 ohms to keep your audio clean, and make sure that the speakers are thumping properly. This of course makes for a bigger expense, but, if you maybe play out live sometimes and need a power amp for that application, you would have this seperate, high wattage amp available to you.
Good luck.
Ed Rei
Echo Star Studio
www.echostarstudio.com