Looking for a server + enclosure

Hello everyone.

I have managed to read a lot of the recent top posts, as well as some blogs linked in the Wiki page. But I feel now I have to ask some questions because I'm a little lost :)

I'm looking for a 1U or 2U (rackable is the word ?) server to run a few linux VM, or at least a few docker containers that would be :

Host : Linux, probably debian or a debian derivative. OR, fedora once the version 24 is stable.

1. DNS server
2. Email server
3. Email list server
4. Hosting : Cpanel for around 10 small websites
5. postgres/mysql container for the hosting and other things
6. a built server, probably instrumented by Jenkins
7. A general 'NAS' container to connect to my Synology (8TB) probably with iSCSI

My budget : $600 for the server. I think I need an enclosure to protect it from the house dust, as well as make it more silent, no ? Also to put my router, FTTH modem and switch.

So, as far as I have read, the best would be a PowerEdge rX10 for example R710. Most people say it's a good model for the low noise and the availability on ebay. The thing is, I see a lot of different configurations so I wonder what to take ?

For this price, what are the 'ok' xeon/i5 models I should select ? Considering using docker, would 64GB enough for all the things I want to host ?

And last, could someone give me some information about the 'cases' I could find on ebay ? Thanks !