Choosing between active opamp filtering or an LC filter
The most effective filter for receiving the magnetic part of the EM spectrum with a loop antenna is a tuning capacitor right across the input coil. It: -


Minimizes unwanted large signals being amplified
Improves the signal to noise ratio because you can "peak" the tuning right at the input
Works at rejecting above and below your desired 5 MHz operating area
Can be easily controlled with a resistor to adjust peaking/rejection of out of band signals.
Can probably be tuned with a varactor diode across a few hundred kHz.


Adding more filtering along the way might also be desirable but please consider input filtering first.