Inexpensive streaming amplifier

SVS Prime Wireless Pro might be an ootion

Stream High-Resolution audio wirelessly via WiFi, Apple Airplay 2 for iPhones and iOS, and Chromecast for Android phones and other devices. Connects directly to your TV via HDMI and features ample connectivity and control options. 200-watt (50 watts x 4) amplifier and precision tuned electronic crossover deliver powerful dynamics, deep bass, and stunning clarity.

I think only one person gave the proper response. Go with an AVR from Marantz or similar. Way more functionality than a Powenode. In fact you get the Marantz NR1510 for $600 which gets you streaming capabilities across multiple platforms, multiple input options for HDMI, digital input, phono, CD, etc. The Marantz also has Audyssey room correction so she can fine tune her 2.1 system and be able to expand as she desires up to 5.1 for less than the Powenode. As you say, she's not an audiophile. And an AVR expands the experience to have a modest home theater set up by getting her a . The Powenode does one thing well. She needs more flexibility for an apartment dweller. 

Nokia Streaming Box 8000 (HDMI connection to TV) and a Denon PMA-50 amp (or a Marantz CR-611/612)

https://www.mynokia.com/streaming-devices/nokia-streaming-box-8000/

https://www.trustedreviews.com/reviews/denon-pma-50

In addition to the various wired inputs, the Denon amp offers BT aptx. Could be a nice feature using a tablet or a smart phone when you are 'on the move'.

The Denon and Marantz amps will drive the Wharfdales with no issues, faire and square

I am using this combo as my second system.

Check out Crutchfield. They should have some good options. 

Get a PS Audio Sprout 100 integrated with an external Apple TV 4K box and your system will sound better that the Powernode and the Apple TV 4K piece will give you more flexibility for streaming music and tv. This is the setup I use in my living room to stream (using Roon) and stream YouTube tv, paramount+, philio, Netflix, and more