There is no significant difference between 1600 and 1866 in real-world use. There is, however, arguably a difference between using a single stick vs dual channel. The 2x4GB would theoretically give you a performance boost over 1x8gb. So going with dual channel AND doubling your RAM certainly wouldn't be a bad thing. I've honestly never tested this out, but you could google for some test results for dual channel vs single channel.
The vengeance cost more because it's Corsair, and because it's Low Profile. And because RAM prices are up since Q2 of this year, and the pricing is all over the place across brands. Still, with the promo, that's not a terrible price for 16GB of corsair. And if you're using a big heatsink and fan for your CPU, the low profile might come in handy.
I have no experience with the Team Vulcan brand. I tend to avoid brands that aren't automatically associated with RAM. Reliable RAM brands include Corsair, G.skill, Mushkin, Kingston, Patriot, Samsung, Crucial, etc.
Do you have a need for 16GB? If not, then none of your choices are really ideal. a 2 x 4GB is what you want.
For 2 x 4GB at 1866, I'd get this: LINK
With the promo it's only $4 more than that single stick of 8GB from G.skill. Dual channel, tighter timings, solid brand.
And I'll say it again, at the risk of sounding spammy, I have 2 excellent 4GB sticks of corsair vengeance I'm selling. 1600Mhz, black heat spreaders, 9-9-9-24, 1.5v. I'll sell them for $45 shipped or $40 local pickup (the extra $45 is to cover paypal fees and shipping). It's this RAM: LINK
This post was edited on 7/12 at 12:08 pm