How low do those speakers go in ohms? As others have said, the 300B is usually used as a SET - and then limited to 8-16 wpc. The latter value is seen in parallel configurations. I recall seeing a push pull 300b design but can’t recall the maker. I have a Tektron integrated that uses 2-4 300b’s and gets 16wpc with 4. Highly recommended. That being said, it also can take 45’s, 350’s, 2A3s, and equivalents. I got it for the 300b’s, but after some swaping I found I preferred the 45’s. I would listen to a few options before committing to a tube type.
If you do go the parallel route, keep in mind the cost. A high end 300b tube can get over $1,000. NOS is off the table due the popularity, matching requirement, and stigma behind it. If you can’t individually bias the tubes and need to replace a matched quad, then when 1 tube goes bad you’re in for a $4,000 bill. I have over 60 tube bed across 3 systems. I wish someone had told me that when I started