You have to be the judge of that. To me personally, you can't have too many. Now the utility of a 5" over a compact is probably more subjective to some and there is clearly a need for others. It all comes down to how you want to spend your $$$$$!
Agree with apipeguy. If you have to carry hardcast FP, Underwood ammo has a 255gr HCFP. You do have a lot of penetration w/hardcast so bear that in mind w/background of target.