The short answer to your question if I understand correctly what it is you are asking is no
It would benefit you to better understand how the PowerCAB works and what the SB3A is.
The longer answer is that unlike the 'dumb' PH ProCAB, the PowerCAB has it's own, -for want of a better description, mini-command station
inbuilt, so it doesn't require a separate Command Station or integrated Command Station/booster like its 10A and 5A siblings. But, isn't there there's always a but? You can't put 5A into it. It is designed to work with an absolute
maximum input of 2A, or it may be 3A ...I'd have to cross check spec, but no more
. The PowerCAB's supplied PSU is rated at 1.35A, peak 2A. If you put more than spec into it you'll fry it.
Enter the SB3a.
The SB3a is a combined 5A booster and command station
just like the 5A PowerPro, but a cut down version with less features. That's why it's marketed as a "Smart Booster". The now also 5A dumb booster DB3 lacks the command station part, so you can't use it with the PowerCAB's powered command station function because of that input current restriction, and it has no 'brain' of its own. You can use the SB3a because when you plug the PowerCAB into it, you use the 4 wire coiled cable so it behaves just like a 'dumb' PH ProCAB defaulting its CS function to the CS part of the SB3a. Clear as mud?
Unlike PSUs where output is seen in as its VA output spec by any brand booster, with controllers and command stations (abbrev CS) each manufacturer, eg: Lenz, NCE, MRC, Digitrax use their own proprietary connectivity, system functionality and bus protocols, so you can't use an MRC or LENZ controller interchangeably with an NCE CS and vice versa?
If you want 5A available to the track with your PowerCAB, the SB3a is not your only, but is almost certainly your cheapest option. Do you need 5A?