I can only speak in the most vague terms about the the options you offered.
Cisco ASA 5505 - I looked last year, and Cisco was expensive. Don't know if that has changed. I have used Pix and was continually frustrated trying to make adjustments. I believe it can do all that you ask, but features are separately licensed. No one was ever fired for buying Cisco.
Juniper SA 2500 - I have never used .. when I was looking last year Juniper was also expensive. My brother is a network security architect at a huge company in our space, and has installed Juniper and has nothing but good things to say. Not sure if it can do VPN; it might do static VPN but not client VPN.
Citrix Access Gateway, Sonicwall 2500 SSL VPN - these are VPN only; they do not replace a firewall. I imagine both are excellent; the companies both know their stuff. I have used a SonicWall firewall, but (see below) I found Astaro to be a better choice.
Since others have offered alternates, I will whole-heartedly recommend the Astaro Security Gateway. I deployed 5 last year to replace Cisco Pix in a WAN, and it was smooth and straight-forward, including multiple site-to-site VPNs and remote access.
As to remote access, the ASG has both SSL VPN and IPSec VPN. I have used the SSL VPN (which is based on OpenVPN) successfully. I don't know about the IPSec VPN, but would be confident giving it a shot based on my experience so far.
I deployed the ASG appliances, but they also sell it as a software bundle to use on your own hardware, and offer a trial. The hardware requirements are surprisingly modest - Intel Pentium III 900 MHz, 512MB RAM, 10 GB hard disk drive.