firewalls

i am looking at thinking of changing firewalls currently we use a DLINK firewall. The talk of Sonicwall TZ 180 totalsecure 25 came up but at a cost of $800.00 i do not know if this is what we want. We are a small company total of 15 so we do have a large it center. If anyone has some ideas of a good, easy to manage and deploy firewall i would appreciate their thoughts.
Thank you