Cisco Firewall :: ASA 5505 Capabilities?

I'm currently looking at the slew of firewall options out on the market. I have the task of recommending one for a client that has the most functionality for a reasonable cost (preferably no more than $800). I typically would go with the ASA 5505 w/base lic. I have been using ASA devices for some years now and they have been great. But, as with the ever changing internet and security threats, would I be ok in going with the ASA? I'll admit I'm not knowledgeable in all the capabilities of the ASA. Is it considered a "Nex-Gen" firewall? Where is the ASA ranked in comparison to the other options like SonicWall, Juniper, Fortinet, etc.? I've worked with SonicWall and Juniper, but did not like them. It has been sometime though, so maybe they have gotten better.
 
With having layer 7 filtering and IDS/IPS capabilities, one feature I will need is VLAN capabilities and ability to provide separate DHCP service for each VLAN (ASA can do this). I will be setting up a guest, internet only, network. VLAN trunking would be nice (ASA can do this with security plus lic, expensive though). In addition, having solid VPN capabilities (client and site-to-site). Good product support and documentation is a must too.