No worries! To expand a little bit about the difference between a reg. +2 longbow and THE Silver longbow, it starts with the damage- 1d10 instead of 1d8
crits on 19-20 instead of just a 20
The "holy" modifier simply adds 2d6 additional damage to evil-aligned mobs (few of those running about

)
I digress, the bow IS made from silver, so
should bypass DR.
The reason I would steer you this way, as opposed to worrying yourself about the metalline arrows, is your DPS will be more effective with the Silver bow and say +5 flaming/holy/acid/frost arrow than the metalline would.
Also, to qualify, are you primarily ranged, 50/50, or primarily tempest?
If you have ANY melee capability, you would be more effective with metalline hand weapons, IMHO.
Hope this helps.