I'm a 95% 4-string player so I'm probably not the best person to give advice on strings for a 5-string bass, but I have a feeling you might be happier with round core strings with 45-130(ish) gauges.
This will give you a more supple feel under your fingers than similar gauges with hex core strings, but not as floppy as 40-120 with hex core strings. (You current Magma strings are hex core).
Some hex core strings with a thinner core can also give you a more supple feel. Dunlop Super Brights is the most extreme example. They actually feel more like round core than hex core.
You didn't say what kind of tone you're looking for but here's a couple of suggestions for roundwound strings with a more supple feel than most (I'm not sure if all of them are available as 45-130 though).
From bright to mellow:
-DR Hi-Beams - Bright tone , stainless steel, round core.
-DR Sunbeams - Nickel plated steel, round core, basically Hi-Beams with a warmer tone.
-Dunlop Super Bright Nickels - Hex core but a thinner core and a more supple feel than any other hex core stings I've tried. "Super Mids" would be a better name IMO, as they're really not that bright once they're broken-in, but have a rather characteristic "growly/nasal" quality in the mids.
-GHS Balanced Nickels - Pure nickel, wonderful warm tone but they work best for soft-to-medium playing IMO, they kinda choke when digging in hard fingerstyle.
All of these strings should give you a more supple feel than similar gauge hex core strings, but not as floppy as "one step lighter" gauge hex core strings.
Of course it's impossible for anyone except yourself to know what kind of strings will work best for YOU, but I can't think of anything else that will give you a "feel" that's kinda between 40-120 and 45-130 hex core.
Some other options are the DR Pure Blues (round core) and Dunlop Super Bright Steel (hex core but presumably the same thin core as the Super Bright Nickels) but I haven't tested these so I can't comment on the tone/feel).
IMPORTANT: IF you get round core strings, make sure you know how to install them. Short version: You need to crimp or bend the strings 90 degrees before cutting them, or the wrapping may unravel. Search this forum for more details.