If you keep what you have the risk of choosing the $40-50 Netgear WNDR4500-100PAS N900 is minimal. 450+450 is an upgrade from your 300+0 but is not bleeding edge expensive.
Not that you ‘should’ but, you could install DD-WRT (beta) on that model. Someone likes it enough to make 3rd party firmware available for it.
FYI I spent way less than you indicated for my routers(less than $100 refurbished from Amazon) and they both have at _least_ one USB 3.0 port. Not suggesting they are suitable for your calendar/application/budget they are old.
I also have a TP-Link AC1900 Smart Wireless Router(less than $100 NEW) that is _NOT_DD-WRT_friendly_ but is/was a good value IMneverHO.
I don’t advocate for China manufacturers but I rarely automatically eliminate them. I don’t trust anyone!!!
I have tried many known exploits on the TP-Link products and think they are just as risky as the next one. Many of their products are also DD-WRT friendly just not the model I mentioned in this post.
They are almost all manufactured in China and ‘they’ have compromised many major well respected manufacturers products during final assembly and testing. It is one reason among many that people install 3rd party firmware(that might also have a buried exploit).
It sounds to me like you are well on your way to being satisfied with whatever you choose.
While I was able to use my present Netgear router efficiently enough, I needed something newer. My present router is over 10 years old. It also has USB and SD card ports on the back. While I won't put highly sensitive on either, it will make for a good central depository to share files on the network.
For me, dollars mean a lot because I don't have much to spend. So I hope and pray that the new router is worth the $135 I spent.