My $.02: Any Intel Mac will be obsolete sooner than any Apple Silicon (M series chips), macOS will stop supporting Intel and Intel applications will stop being released at some point. And, an M4 is overkill for watching video, browsing and sending email.
I'd suggest returning the M4 and buy a M-series computer with 16GB RAM and at least 512GB storage from the Apple Refurbished Store (not Amazon or BestBuy). They are refurbished by the Apple and come with a full one-year warranty, 90-days of support and is eligible for AppleCare. I see a M2 Pro Mac mini 16/512 for $1099 on the refurb store or $1049 for a MacBook Air M2 16/512 (you can get it for a little less if you are a US Veteran).
Either would be perfect for your use and give you many years of supported use. Then invest your $500-$550 savings in a 4K or 5K 27" monitor with a USB-C connection.
Also, you can change the size of items on your iMac display using System Settings->Display and adjust the slider in "Use as" section.
Lastly, you likely can attach your old HK speakers, keyboard/mouse and maybe your Newegg display to your iMac...
I'd suggest returning the M4 and buy a M-series computer with 16GB RAM and at least 512GB storage from the Apple Refurbished Store (not Amazon or BestBuy). They are refurbished by the Apple and come with a full one-year warranty, 90-days of support and is eligible for AppleCare. I see a M2 Pro Mac mini 16/512 for $1099 on the refurb store or $1049 for a MacBook Air M2 16/512 (you can get it for a little less if you are a US Veteran).
Either would be perfect for your use and give you many years of supported use. Then invest your $500-$550 savings in a 4K or 5K 27" monitor with a USB-C connection.
Also, you can change the size of items on your iMac display using System Settings->Display and adjust the slider in "Use as" section.
Lastly, you likely can attach your old HK speakers, keyboard/mouse and maybe your Newegg display to your iMac...