Your decision will depend on your budget and which features you want (i.e. IPSec and SSL vpn, IPS, etc.) and how much scalability you want.
You can look at the ASA5510 p/n:ASA5510-BUN-K9 or at a Cisco 1841 p/n:CISCO1841-HSEC/K9
with any of these devices you will probably require a switch.