X-5 is probably my best mech overall (which isn't saying much), but I go between;
4x SPL/2x SRM4
2x ML/2x SRM6
Pre-missile tube buff I used to do SSRM + 4ML
So far I tend to run out of ammo right about the time a match finishes up, so 250-300 is ideal for the SRMs. Works great as a flanker/harasser/buttpoker and is fast/durable enough for those moments when you need to get in to finish a target and get out before you get focused.
Used to play exclusively conquest mode with it and it was a great cash cow.