45-100 is my preferred gauge, but I have a fair amount of variation on my four basses. I range from TI flats on a Jazz to Light Steels (40-100-128) on a Sadowsky to medium light DA XLs on a P (45-100) to Superalloys on a G&L L2K (45-105).
IME, string gauge does not necessarily make your tone thicker. Brand of string, EQ, bass, amp, cabinet all have an impact. All nickel rounds are not equal either.
Based on what you describe I would recommend TI Superalloys. I have played them on an alder / rosewood 5 string Jazz and on a ash / maple 4 string G&L L-2000. They sound different on the different basses but they have a very nice low mid punch that may be what your after. Or maybe not.
Superalloys/
Labella Hard Rockin' Steels are a great steel string with a nice mid voicing, tight bottom, and non harsh highes. A bit different than what you are probably playing today. They are my preferred string on my alder / rosewood Sadowsky.
Also try playing with the boosting mids in your EQ. I prefer a bump around 800Hz. But some bass / amp combinations may benefit from a boost in the 200Hz region. If you have the smiley face, try and get away from that. Set bass and treble flat.