So my players have been complaining about SR on the creatures, and now have been researching and want to do the following.
Purchase Piercing Metamagic Rod, 3000gp, Lesser version and also some Dweomer's Essence.
If they get both, can they use them together to get +10 vs SR?
Yes, they stack. It's not too much of a problem though, since they only stack on spells less than 4th level and it costs 500gp each time they do it, a maximum of three times per day.