Need help with LAN Architecture - ASA/IPS, and ISR placement

Question

Dear friends, I am new to Cisco community, had no previous experience with managed networks and desperately need an advice setting up a LAN for my small business. Here is what I did so far:
ASA w IPS is facing internet, has a webserver connected to DMZ and then ISR on the inside interface. ISR is used for running CCME/CUE VOIP and VLAN NAT. Switch is connected to the ISR with a trunk interface. I setup multiple VLANs with ACL to separate engineering/management/sales/fileserver. Inter VLAN routing is enabled on the switch to allow Gigabit routing from the Fileserver VLAN to the Engineering VLAN.
I know this is probably overkill for a 4 people company, but my objective is to be ready for possible attacks form both outside and inside and to ensure business continuity and minimal service interruptions.
My question, would it be more practical to connect ASA directly to the switch and do VLAN NAT on the ASA instead of the router? This way if router fails, I loose VOIP but not Internet and if ASA fails, I only loose internet, while phones will stay operational. This approach should also let me use ASA IPS to monitor inter VLAN traffic, so if 1 of the user PCs gets infected, hopefully IPS will contain the damage to a single VLAN.
What would experienced network architect do in my case? Any suggestions?
Please, forgive me if I misunderstood something or did something silly, as this is my first network setup (not including household grade routers)
Thank you very much in advance!

Answer 1

Thank you for your response!
I still keep debating if it has any advantages to use a Router in between ASA and the switch, or should I connect switch directly to
ASA, so the only function of the router is to run VOIP?
I saw multiple network diagrams which all had a border router, then ASA then switches. In my case router runs VOIP and I would want it to be behind ASA. Any benefits of running internet traffic through both ASA and a router?
For redundancy, we can’t really afford 2nd ASA at this time, for now I would want to make sure there is as little chance as possible that both phones and internet go out simultaneously.