I don't understand the previous posts.A JBL Summit 300 is a very high effecient horn loaded speaker it should not require very much amp power at all unless you want night club disco levels at 200 watts per channel.50 watts per side should be more then enough.I suppose it depends on the type of music you listen too,and your listening hubits.
I use to own a pro 4 way JBL 4343 which was a step up from the 300 Summit and I had to sell it because it was just putting out to much SPL Levels in a home situation.At the time I was using a Marantz 4400 Receiver in Stereo mode at 100 watts per channel which was to much for a home listening room IMO.