You might not be able to play your system at very high volume levels, but, for the VAST majority of the time, 4 watts will be plenty. Most of the time you will not be playing above a quarter to half a watt, and even if you occasionally push toward the 4 watt level, this would probably be only on peaks, and if there is some distortion or compression, that is just one of the compromises one makes with ANY component choice; none are absolutely the best under all circumstances and conditions.
I personally like the sound of 6L6 tubes, although I have never heard them used as a single ended triode tubes. Given the low price of the amp, it would not be easy to find other higher power alternatives to recommend. I have not heard the amp you are considering so I don't know how it would compare with your Cronus amp.
Even if you have little skills at building gear, you could probably build an Elekit 300B amp; the kit comes with very good instructions and you can learn basic assembly skills on Youtube. The amp would cost a bit more than $3,000 once you add in the price of the 300B tubes (the kit comes without tubes), but, I've heard that amp and it is pretty good, and puts out a little bit more power than the amp you are considering.