Although AMD currently still is the best performance per dollar, buying into any of their current product lines now is a dead end. At least that's what I've been told, since it's rumored that Athlon X4, A10 APU's & FX won't be compatible with AM4 Motherboards. Likewise I don't think they'll be making anymore new CPU's for those past generations. If you need to build something right now I'd say go with an i3-6100, they're about $120.00 & can pick up a decent LGA 1151 motherboard for $50.00 or less. That 2 core, 4 thread CPU by the way is significantly better than an Athlon 880k & even an FX 6-core.
Every socket right now except AM4 is dead end. Current DDR3 supporting CPU's are not compatible with AM4, it's well known fact, no need for rumour. Also AM3/FM2+ will not receive new CPU's as Zen will supersede them.
i3-6100 is only dual core and paying over $100 for dual core is no if you ask me. It has no match for AMD six core if all cores are used. Even quad core i7 has no match for AMD octa core on medium to heavy use (like virtual machines).
So- there is no equivalent to an I7 processor in the AMD line of products?
Depends on what i7. i7 may be dual core or 10-core.
In any case, Zen matches Intel's offerings clock to clock on "most applications". Clock speed will probably be lower but so is power consumption also. Zen also will not match Intel CPU's when using AVX-512, but that feature is mostly useless anyway and power consumption is huge. Putting full scale AVX-512 support for 95W octa core would mean very low clock speed. Best Intel can do at 140 watts is 3.2 GHz.