Hello the greenman! You're thinking creatively and that's good. My own system uses eight channels of amplifier for a pair of four way speakers. Each speaker has it's own amp - but - I use an electronic crossover, so each speaker (tweeter, upper mid, lower mid, and bass) has it's own amp. Your suggestion proposes four amps for two speakers if I am understanding you correctly. Doubling the power to a speaker only results in a 3 db increase in volume in the room. You won't get much "bang for the buck" that way. I have several low wattage amps - all sub 10 watts. I find I can play any speaker system in the house with a single set of input posts to satisfying volume with any of them. If you want to play your music loudly, that's where you need POWER. What I would call "normal listening levels" seldom exceed five watts. If you want to play at the actual sound level of real combo or orchestra in your listening room - so you can't hear the phone ring, or your partner calling you to dinner, or the baby crying - you may want more power, but not just a little more. To hear your music 10 db louder, you need an amp with 10 times the power of whatever the starting point is. If you have watched power meters dancing on the faces of expensive amps, you know a 10db difference only sounds three or so times louder. So . . . now you know why lots of folks like the sound of 100 watt + amps.
You are unlikely to do any damage by using you 300B amp to drive your speakers directly. If you run out of power, the sound will just become unpleasant, that's all. If heat problems worry you, use one of the really fine class D amps out there. I use three Starke Sound AD4.320 amps on my main system which uses 11 channels of sound. It is big, heavy, and non-descript but it sings like a choir of angels and costs less than $1500.
Four 200 watt channels for way under two grand. The best bargain in amps! As good as the fancy NADs which are getting great press.
Just be sure you are using decent speaker wires (14 gauge zip cord for starters) to get your 300B's output to the speakers. Yours are efficient enough to a good job with 8+ watts. I have filled a huge room with background music for a fancy dinner with a nine watt class A amp driving Magnepan 1.7i speakers (notoriously power hungry). Don't let anyone talk you out of being happy with what you've already got! Enjoy the music. If it doesn't play loud enough, get an amp with at least 10 times the existing amp's power. If you want to roar - 100 times the power. If you go that way, be sure you can afford speakers that won't catch fire when their voice coils melt! Enjoy your music. If it sounds fine, buy music, not electronic gear! Remember, in the early days of quality audio, 20 watts was considered a lot of power.
Keep Smiling!