Hey Blommen, yes that was my impression. I compared the Crack+SB and the Espressivo, using higher-quality-than-stock tubes in both. I believe I had a Mullard CV4003 input and Western Electric 421A output in the Crack+SB and Western Electric JW 2C51 input and Foton 6N6P-IR output in the Espressivo. These are nearly the best tubes that can be put in each respective amp.
Of course, it all depends on what you value. For me, the most immediate and high-priority item when comparing amps/tubes is airiness/staging/separation, which lends it self to detail-retrieval as well. The Crack+SB was just more spacious, larger soundstage, and thus, more detailed sounding than the Espressivo with this setup. The Espressivo had a much smaller stage, with sounds/instruments more on top of one-another.
Now if you can sacrifice some soundstage/air and detail for preamp out, that is your call! But I could not overlook it.
Now you do not need a Western Electric 421A to get that airiness, a Tung Sol 5998 will get you 90% of the way there. A decent 6SN7 with an adapter will also be an upgrade over a Mullard CV4003 in the driver position, IMO.
Hope that helps.