....if you've got that spare Mac, you can run your existing Quicken on it as it stands.
I still have my last Mac (for the grandkids to use) and I considered your suggestion - thank you for it. However, the thought of booting a slow-to-boot separate machine every time I want to enter a credit card expense....... Also, I've only kept that machine because it has an audio input which is, through Bluetooth, the only way I have of getting some stuff to my 27". If I locate a mini recorder with Bluetooth, or a good Bluetooth transmitter, I'll give the 21" to the grandkids to take home.