16GB i7 is pretty insane for data mining.
unless u are planning to share the desktop between multiple users and/or want to install multiple database in this.
here is one tip: if you want maximum database performance. max out the RAM to 64 GB or just 32GB and prepare a 16+GB RAMDisk on it, then you will have to install you databases in this drive. As the result, instead of accessing database from the mechanical disk, it will be accessed from RAM itself, with 20-30x speed of the HDD.
u may also want to buy a good ssd for storing the RAM disk image file, but don'[t forget to take regular backups, because everything being in RAM, will be lost if the power goes down.