When you search for a spartan 3e 500k starter board you see either Ebay
used (abused?) boards for anywhere between $90-$100+ and new ones (maybe) at over $400. You can see what tying to buy an obsolete part does for the price.
If you look at a Artix-7 35T Arty board it's currently ~$124 (used to be $99) for a brand new board from a big distributor. Avnet/Mouser/etc.
Spec wise the Arty is a much better part.
More slices 5200 vs 4656, besides being all 6-input LUTs instead of 4-input LUTs
Way more memory 1,800 Kb vs 360 Kb.
More user I/O 250 vs 232
DSP48s (90) vs multipliers (20)
More clock resources 5 CMTs vs 4 DCMs
PCIe core vs none
GTP (high speed transceivers) vs none
XADC vs none
AFAIK, Greece (listed on your profile) isn't on any ITAR restricted list so you should be able to buy one without too much of a problem.
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To answer your questions...
1. probably as the bit rate of voice is rather low 96 Kb give decent results and the FPGA logic can run in the 100's of MHz so you can do a lot serially if necessary.
2. probably can do VGA or something similar, I doubt it can support HDMI or HD resolution given the lack of memory on the board and in the part.
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Update: It appears Amazon is selling them for Digilent for $99 still.