You have a Roku 1. There was a noticeable difference between the Roku 1 and Roku 3 performance when those items were the current items in the Roku lineup. That is not the case between the low end and high end devices today.
I'm going to recommend that you choose a Roku based on its features. Performance will be similar regarding the items you listed. Look at the other stuff, and pick based on those items and how they appeal to you.
I had Roku Premier 4K but it was too slow and had buffering. It has basic remote which needed to be pointed exactly to the device.
Now, I am using Roku Streaming Stick+ which is also 4k. It has the wifi remote with volume control and voice search. The device itself plugs directly into the HDMI port on the back of tv, so it is discretely hidden.
However, as we are getting summer temperature, the device gets warm and starts freezing. Roku offers a complimentary HDMI extender to keep the device a little distant from the tv. The Roku Support page is broken and does not allow ordering this. I am waiting on Roku Support to get back to me.
Other than this issue, Roku Streaming Stick+ is a perfect match of price & performance.
I believe you mean the Express 4K, not Express 4. I have the Express 4K+, and it's certainly a well performing player, and is a near match to my Ultra 4800. Of course, the Ultra also supports Dolby Vision and the new AC-4 audio codec. But even my older Ultra 4640 is still perfectly sufficient. Any current model Roku should work far better then your current player.
You mentioned network connectivity. The only Roku with a wired network connection is the Ultra. The new Express 4K players support 3rd party USB Ethernet connectors, but they aren't included. Officially, only the Express 4K players and the four versions of the Roku soundbar supports the USB network adapters. This page describes how they work and the approved adapters.
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