Ideally I'd like solid state on the low end and tubes on the mid-high but dunno if my L220 crossovers can be used in biamp.
Regarding your shopping list: It's unclear if you noticed, that amplifier boards do come in pairs, so you only need to order one "item" from the shop.
You are missing jfets in your list I think. Either buy LSK one's from DiyAudio shop, or use one of the proven sources -don't buy blindly on the internet.
It seems possible that you could modify the L220 crossover so that the LF section was one input and the MID/HF is another. Here is the schematic (from audioheritage.org)
View attachment 927809
You could start with one Firstwatt (Aleph J, F4, F5, M2, F6... etc) and build a second Firstwatt later and have biamp mono-blocks.
So, let's try with another Italian GO FOR ALEPH J, F4 OR M2!!!
This is the way I'm going to follow
Beauty of a First Watt amp is once you have a case / power supply, you can just swap in amplifier boards to find out what you really like with your ears, room, equipment, source material, etc... F5? Aleph J? M2X? Just swap it in... (I obviously like the F4 and then just roll preamps of different flavors..)
We are 'talians from the south, harder than the others to convince...
So which would you pick as easy to start with and eventually upgrade later of if confident with the assembly and result?
I'd go for J or F4, absolutely keepers, even if you would switch to other FW boards in the future
Okkey Peppí I will give a read at the F4 specs but since I am no tech would you mind as a fellow Borbonic to summarise for me pros and cons of j4 vs F4 vs F5?
F4 would allow full potential of your SP9 to shine, simply because F4 is not having voltage gain ....... that means that for full blast , preamp must deliver that on input of F4
that also means that F4 is not having much character of its own, resulting that preamp is dominant in amplification chain, sound wise