How to Obtain Enterprise Level FIrewal on a Budget

Just Like everyone else I'm trying to see if that mid point can be found....
A high performance Non Blocking Router / Firewall with more features you can shake a stick at a fraction of a cost of similar enterprise units !

Here's what i have so far...

Manufacturer HP
Manuf Model DL360 G4
Processor Type TWO x Xeon 3.6GHz/2M/800
Processor Speed 3.6 GHZ
Memory Type 8Gb DDR2 PC3200 ECC REGISTERED
Memory 8.0 GB
Hard Drive Size TWO x 72.8GB 10K SCSI U320
Network Card 2 x 10/100/1000GB Ports Embedded
PCI Slot #1 Dual Port 2GB SX
PCI Slot #2 Empty
Case Style 1U
OS NONE
Optical Drive CD

Cost - $175 Locally through classifieds

Planning on adding a Wireless N card into it.
The cards I'm tied in between the following cards:
- TRENDnet TEW-623PI v3.0R
- D-Link DWA-552 PCI
- Netgear RangeMax WN311B

They all are capable of 300Mbit and Wireless N, however the Netgear has the advantage of coming with a high gain antenna as well. However a higher gain antenna can be purchased separately I guess.

Cost ~$75

And now down to the software !

What the best software to use for routing / bridging functions as well as DNS Server and FTP and TFTP Server functions ??

Currently on 250Mbit service through an DLink DIR 825 with DD-WRT with tweaks and over wireless i dont see more than 22-25Mbit/Sec and 45-60Mbit/Sec when wired in.

Direct to modem can pull 180-220Mbit !!!
Need to eliminate the bottleneck in the system. Also streaming movies off the server gets choppy when the kids are on Netflix. Server has Dual ( CAT6 ) 1GB feeds into the router from each Switch. Hence why I don't mind the upgrade to dual 2GB fiber when my server already has it

Server is a HP p-Class Loaded Blade Chassis with an Attached 20TB SAN ( 12 x 2TB SATA 3 Drives )

Some options
http://www.untangle.com/
http://www.smoothwall.org/
http://www.xorp.org/
http://www.vyatta.org/