I don't think they will be sufficient - certainly not $50 ones.
Why not? Acquiring 4 ADC channels to DDR3 memory doesn't require a lot of logic. The limiting factor is the number of pins. What Artix have you used on your last board? What was resource utilization for your MIG?
Of course, if there's some sort of data processing besides acquisition, this should be accounted for.
for now, the paid $4000 quartus SW is not justifiable for a one-off that probably never see the light. so using an FPGA that doesnt require software license is much preferable. earlier i said the FPGA probably will perform FFT as well, but if this means requiring larger FPGA with multi thousand dollar license, then i think it should be beneficial in term of cost to off load the FFT to MCU processing, Arm V7 1GHz quad core or the latest 64bits Arm A53 can be hard at cheap, or maybe even adding 2nd FPGA specialized in FFT alone, this... mmmv (my milage may vary). now i'm not sure on licensing scheme of other brand like the mentioned Artix KIntex etc, but if the cost of the license is near 4 digits cost then i think they have to be discarded from the list, for now while the money is still peanut small...
...have several ADCs that sample data in an interleaved way, so that each one can sample at lower effective sample rate.
yes i should have said interleaved, instead of "staggered"
We already had digital scopes with 8 or 16 gsa/s almost 20 years ago (see the DDA series of Lecroy scopes for instance) and this is how that was done.
exactly except they are proprietary, and the components cost back then i believe is unachieveably expensive by hobbiests during the time...
today, what is unachieveable is the sw license cost
people just know how to get money. its understandable for FPGA development tools because they have to cover R&D and production factory, but look at things like EM Solver, the cost is just simply nuts... offtopic.