In the last election, the NRA poured money into the campaigns of eight senators. Seven lost.
"Money and Senators" is irrelevant to the issue of "Representatives and voters".
Every Congressmen in a rural district who crosses the NRA will be voted out of office. It will not involve any money. It will only involve the NRA advising their members which candidate is the best on guns.
Also, there is a bit of a difference between "an election year when NRA voters have not seen a real threat to their rights in over a decade" and "an election year that was preceded by a high profile assault against the Constitutional rights of all gun owners".
NRA voters may have been snoozing in 2012. But they are wide awake now. And if there are any grave violations of their rights, they will be very wide awake in 2014.
And while senators may be a bit harder to topple in a statewide election than congressmen who are limited to rural districts, you might want to pay a bit of attention to the Democrats in the Senate. They seem to fear the NRA a bit more than you do (possibly because they are the ones who'd end up voted out of office).
The Senate Democrats have no plans to pass any ban on assault weapons, and they are not even going to try very hard on magazine limits.
And while they are going to try to pass expanded background checks, they are almost certainly going to take the NRA's concerns into consideration when they draft the legislation.