Hardware Sizing Guidance

[danesco]

I was looking the guide http://www.pfsense.org/index.php?option=com_content&task=view&id=52&Itemid=49
But i still have some questions  :-[

Im looking to buy this alix kit from netgate to manage my network http://store.netgate.com/ALIX2D3-2D13-Kit-Silver-Unassembled-P175.aspx
My requirements are:
Maybe 2WAN Load balancing (1.5Mbps each one)
DHCP Server / Firewall / Captive Portal (With voucher config)
Or according to certain tecnhical things a Squid without caching, to do ACLs

The theoretical maximum number of clients is 160, now there are 80, but on average 40 or 50 are connected.
So, with this especific needs, its enough the alix server?. Im looking for a tiny power save option because its needed that the server will be in a tower enclosure. (for wireless APs)