will a linear power supply really sound better with my arcam dac

On paper it will but improbable for us to know if you can hear it.
Not to mention the personal value of the expenditure.

Hanky14 - if your system is a high enough quality, a linear power supply (when replacing a digital power supply) is usually easily auditable.
Our Meridian 800 series components easily demonstrate their improved linear power supply upgrades. 

It likely will. As mentioned above, you need a system that is revealing. If you’re spending the money, make sure you upgrade or have decent cables on the Arcam and SBooster or you might be wasting your money. I upgraded from the switch supply to a LPS on my DAC and it made a nice improvement. If you don’t like the SBooster, likely you can resale it and not lose much, but I bet you’ll keep it. Teddy Pardo is what I went with and took two weeks or so to get… much better looking box over the SBooster in my opinion.

Cheaper and way better sounding than a linear power supply is an Li battery pack. They're < $100 and depending on the one you purchase will run your DAC for days on end.