hello Guillermo,
I've found the "problem" with Croft gear to be that the law of diminishing returns kicks in very early. Croft's entry-level pre-amps especially give you a very large measure of his signature sound (for me: 3D & punchy). that being said, I've just had my octal SMA IV upgraded & kitted out with a separate RS PSU. the magic has moved up by a number of notches -- but it was very much there to begin with.
I used to have a modern Micro 25 & enjoyed it a lot. ona whim I then bought a (1990 or thereabouts) "Mega Micro II," with 12 valves in the PSU alone & had it upgraded & found I like its 12bh7a's in the line stage. I then chanced on the SMA IV with its 6SN7's & 6SL7's and there is no going back to ECC83's for me.
I realise all this is not particularly helpful, but I guess what I'm saying is that the Croft tree does not have to be a steep climb & has lateral branchings-off which are not overly expensive to pursue.
I am not a particular fan of tube-rolling as such -- although that is another avenue Croft gear opens up.
btw, what power amp you're using with your pres?
cheers
ahto
Lenco L75 in a very heavy plinth /Hadcock 228 /London Decca Blue /Croft SMA IV Octal with separate 2020 PSU/ Croft 7R monos /Harbeth SHL5
Fletcher .3 /Hadcock 228 / Denon 103R/ Croft HeadAmp /Croft Mega Micro II (2015) /Croft Series 5 MkIi /Markaudio SOTA Cesti B
Leak Troughline III GTA / Vecteur D-2.2 / Wadia 121 / Katana, Isolator & RPi /RFC & AntiCable