This all depends on what you want sonically. I am a convert to the 45 tube (EML mesh in flavor). After trying a hand full of well received 300b amps, and if you can use a small 2watt amp, I think ultimately the 45 is the finest I have heard.
There is the hybrid Tom Evans Linear A or B which is a powerful SET that I feel is very close to a well done 45 amp in its transparency and naturalness but has lots of power.
After having a 45 then going back to a 300b, I found the 300b to be course, slightly unresolved and less natural in comparison. There is something about the bloated nature of the 300b which is fun for a while, but I found the 45 removed thoughts of hifi. Bare in mind my speakers are 109db/watt sensitive, but I think if you have 100db or so speakers you will be fine with the 45.
There is the hybrid Tom Evans Linear A or B which is a powerful SET that I feel is very close to a well done 45 amp in its transparency and naturalness but has lots of power.
After having a 45 then going back to a 300b, I found the 300b to be course, slightly unresolved and less natural in comparison. There is something about the bloated nature of the 300b which is fun for a while, but I found the 45 removed thoughts of hifi. Bare in mind my speakers are 109db/watt sensitive, but I think if you have 100db or so speakers you will be fine with the 45.