Celestions are honest speakers, (so will handle a true 50W, unlike some other speaker brands) but not all are great. Those ones are definitely built to a low price-point. At 95dB, it's not the loudest speaker out there (though probably a benefit with a 200W amp) so don't be surprised if the amp doesn't sound as loud as you think it should. https://celestion.com/product/20/rocket_50/
The trouble with a quad-box is that it costs such a lot to upgrade all the speakers.