It depends on your speakers. If the speakers are efficient enough to handle large scale music with 45s, then they are fine. If you are using a subwoofer with a dedicated amp, and just using the SET for lower mids and up, then you have quite a bit more flexibility, but may have sub integration seams.
In general, I'd say if your speakers go much below 40Hz, then the 45s will be getting stressed to the max, even on efficient speakers. The bass frequencies take the most power to reproduce, and the lower you go, the more power you'll need. Using a sub with its own amp can help this out alot. If you're trying to get down to 20Hz with authority, you are going to be having trouble with the 300B also. It only makes about 8 watts, and that doesn't go too far at 20Hz. But they both will do the frequencies over 40Hz quite well on an efficient set of speakers.
The 300B is noted for its "fatter bottom end", and the 45 is noted for its totally awesome tone overall. Compromises are going to be found in all systems, and you have to decide what is the most important to you.
In general, I'd say if your speakers go much below 40Hz, then the 45s will be getting stressed to the max, even on efficient speakers. The bass frequencies take the most power to reproduce, and the lower you go, the more power you'll need. Using a sub with its own amp can help this out alot. If you're trying to get down to 20Hz with authority, you are going to be having trouble with the 300B also. It only makes about 8 watts, and that doesn't go too far at 20Hz. But they both will do the frequencies over 40Hz quite well on an efficient set of speakers.
The 300B is noted for its "fatter bottom end", and the 45 is noted for its totally awesome tone overall. Compromises are going to be found in all systems, and you have to decide what is the most important to you.