Typical headphone impedance is 32 ohms. 24 is on the low side but not as low as (say) earbuds. So your phones are in the normal range.
I have a pair of MDR-V6’s (the pro version of the 7506) and they are fine headphones with most sources I have used them with. If you want to buy the 7506 and try them, it won’t be a bad buy. They are also relatively inexpensive.