HowtoForge Forums | HowtoForge - Linux Howtos and Tutorials - I need to migrate from mikrotik hotspot to linux hotspot

I have a small IT company, it is going bigger day after day, the services I do offer need to be more efficient as the company goes bigger.

I am using Mikrotik RouterOS to:
* Setup a "basic and easy to manage" hotspot server or pppoe server (for "easy to manage AAA methods") or act as a regular router.
* Bandwidth managment per user.

It is now making me angry, cause it is not doing its job very well as the company services enlarged. So, I need an alternative, doing the same and much more. But, the only condition is: I want it a SECURE open source resource.

So, I wonder if (smoothwall, ipcop, engarde secure linux or any other distribution suggested) capabilities can help do the same job Mikrotik doing for me!
*******

my network is as follows:

I-net gateway caching firewalling etc.: CentOS Linux.
DMZ: DNS CentOS, web CentOS.
Mikrotik RouterOS for what I've mentioned above.

I-net gateway
|
hub----DMZ
|
Mikrotik
|
|
hub ------------------ wifi
|
local net.

thanks alot...