Switch Suggestion for a Small Office (one switch or two?)

Earlier this year I took over the Sys Admin role for a small local government agency. One of the upgrades that I was advised to schedule (by the predecessor) was a switch replacement, but I'm not too sure what to purchase.

The building currently has 2 separate lines coming in, one from the State and one from a local ISP.
The State line is only used for emergency services. The ISP line is used for everything else.

My predecessor used a single ExtremeNetworks POE switch and split the ports into two groups. State ports and ISP (everything else) ports. Currently the switch has a little over 85% port usage. We utilize a handful of VOIP (POE) phones and around 35 end user devices. There will be little need to add new devices to the network in the near future as all the offices are full. Less then half the staff are onsite at any given moment.

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Here my questions:

1. Should I buy 2 switches to replace the one? The network is very basic, no VLANs or anything more advanced. I'm leaning towards replacing the one switch for two but I'm unsure if there really is a benefit outside of redundancy. The State services could theoretically fall back onto the ISP ports in a pinch but would not be a long term solution.
2. What would be some reliable brands for switches? Uptime is a must. I'm only familiar with the Dell OS10 and older HP Networking (non-Aruba) switches.

Any input is appreciated! Thank you!