Fritz Carrera 7 Be and 300B power amp?

At 87db I'm going to say no. In my experience with 300b amps you need at a min 95db to have enough for dynamic swings. also to consider SET 300b's amps really only work properly in the first half of the power delivery they tend to distort fast at the upper levels of their power range.  if your listening at background levels sure but if you want dynamics and a good range of volume for the normal listener then no.  I ran 94db 8ohm speakers on a 300B amp and if I was honest it wasn't enough. only 8wpc but really only 4-5wpc usable IMO. 

Fritz Carrera 7 Be:

There are at least two links on his website that are articles/reviews of his speakers being used with 8-watt 300B amps .

I have successfully run my 88db Carbon 7 SE mkII’s with a 3.3 watt 2a3 SET amp and never was it close to running out of gas.

Remember, it’s that lack of a traditional power hungry crossover that allows the Fritz speakers to sing on just a few watts. The sensitivity isn’t everything. His speakers are a very benign load wrt impedance and phase shifts.

Give John a call and let us know what he says

With Fritz It’s the true 8ohm nominal impedance spec that makes it possible.  I suspect it will mostly have to do with room size and how loud to be able to go more so than the amp can’t drive the speakers well.  

Thanks for your help folks. My room is 13 x 11 with the speakers lined up along the long wall. One of the short sides is open to the rest of the house. So small room basically.

Speaker are 5ft apart and I'm sitting 6 ft away

I used to do audio shows with Fritz where we used the Carreras and Carbon 7s with a 10 watt 300B SET amplifier. The combination worked just fine in a room that was 12' x 19', and we got it pretty loud, even trying to intentionally clip the amp. The smooth impedance curve and the benign phase angles of Fritz speakers makes use with low powered amps, including SET, possible. A lot will depend on the how well the amp is designed, the size of your room, and how hard you are going to push the amp.