No experience with the P90, but look at the MSAR STG-E4. Bullpup that can be purchased left handed and switched, 5.56mm NATO, Stanag mags(common with 556 ER), 2MOA and the same size as the PS90 and SBR with 16" ballistics. Then you can stick to a NATO or common pistol round to ensure you have access to new mags and ammo for your rifles and ammo for your pistol. Also won't break the bank.