Ghosty, my first, instinctive thought when you said you didn't feel there was enough bottom end was to suggest you maybe try (if you haven't already, and I suspect you have) a Sansamp PSA-1 rack.
Maybe a step backwards from your POV, but I wish I hadn't sold mine back in the '90s. I used it for everything including bass guitar and fattening up EDM kick drums, which is why it occurred to me when you mentioned the low-end thing...
i have an old 1.38 version w the buried switch on top
Ive had 2 other top switch versions (a 1.38 and 2.0)
This one I kept sounds clearer and feels better to me for some reason ??
Tubes make a HUGE difference in this pre. Roll some, or maybe slap some RFT or current prod Sino pre tubes in it.. they seem to work best sonically for me versatility wise.