Kind of tough to compare the two unless you've owned & experimented with both. However, as an owner of the Calypso, I can say from experience that the Calypso can be transformed from very average to exceptional with the addition of $500 to $1,000 in NOS tubes, with emphasis placed on upgrading the 12AX7's.
I witnessed drastic improvement upgrading stock & new production tubes to NOS Mullard CV4004's in the 12AX7 slot & Tesla 6922 gold pins. Experienced further, albeit less dramatic improvement upgrading the Mullard CV4004's to the pricey Mullard 10M Gold pins.
I have no need to try a different preamp for the foreseeable future.
I witnessed drastic improvement upgrading stock & new production tubes to NOS Mullard CV4004's in the 12AX7 slot & Tesla 6922 gold pins. Experienced further, albeit less dramatic improvement upgrading the Mullard CV4004's to the pricey Mullard 10M Gold pins.
I have no need to try a different preamp for the foreseeable future.