I don't know the Areca controller
But all my servers are SuperMicro and I'm happy with them.

I'm not running the nss on a supermicro tho, as I bought a ready to run solution and it was not based on supermicro.

Have you tried using software raid just to rule out controller issues?
If you believe it is the NIC try to benchmark it with netcat

something like
cat /dev/zero | nc otherhost:5555
and on the other host
nc -l -p 5555 | cat > file

I believe this will test the NIC troughput independent of the disk performance

also try an hdparm -t /dev/sda (or whatever) to check the disk performance