Opinions on new router for 300/300 fiber service and voip phones on a budget

Years ago a non-profit school I help with tech switched to a voip phone system and the Asus router they were using didn't prioritize the voip phones very well. The voip folks sold them an Adtran 3120. It helped. They are now upgrading their internet speeds from 75/75 to 300/300. The current Adtran 3120 tops out at 100M.

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So...I'm looking for a new router for them. They have 6-8 hard wired computers and about 30 laptops that come in over wifi. They have a computer lab with 16 desktops that seem to saturate the network from time to time when they are all visiting a busy site. Looking for a hardware router/firewall. Their budget is $300-$400 ish.

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Considering a WatchGuard T15, the T35 is a bit expensive for them.

PF Sense SG-3100 firewall ( https://www.netgate.com/solutions/pfsense/sg-3100.html )

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Any others that should be on the shortlist? Thank you for any guidance.

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Sean