Is my memory too slow?

No, I'm sure it runs in dual channel.
Another thing..I can't actually get those modules to run at reference speed, which would be 1600mhz 7-8-7-20 at 1.65v.
I only got 1600mhz 8-8-8-20 at 1.65v...

It won't even boot with the reference 7-8-7-20 timings..
With 8-8-8-20 it's stable, i've ran memtest.

Although I'm inclined to agree with vvhocare5's point that you're not going to notice much of a difference in every-day use, I do sympathize with your concerns. 99% of the fun of this hobby is tweaking this stuff to perform to the maximum possible level of performance and reliability. I wish you luck in getting this up to the bandwidth target you're seeking and wish I had some better answers.

From what you've said about your voltage settings and the level of performance you're able to get, I'd suggest that you have a couple of below-spec memory sticks. You might consider trying your luck at an RMA -- you have a good excuse; you are giving it the voltage it wants and the timings it wants. It should perform at -- or even better than -- the specifications given by the vendor. If they're not, not your fault or the mb's fault -- the process of memory speed spec'ing (namely, binning) has the potential to be fraught with error and imprecision, so getting out-of-spec ram is not impossible unless the vendors are exercising the height of rigor and discipline in the binning process.

Given your experience, they clearly aren't. You've done all you can. RMA time.