I bought the ETS midpipe w/ resonator after installing the ETS axleback (w/ mufflers) on my '24 WRX. Both are very easy to install with supplied hardware and gaskets. The combination sounds absolutely amazing! The resonated midpipe seems to negate some of the annoying and loud drone than with just the axlebacks (there is still a bit of drone around 2,000 RPM). The overall tone seems to be deeper and throatier than with just the axlebacks.
My only suggestion to ETS (and Subie Supply) is to include the proper oder of the supplied gaskets that fit between the downpipe-to-midpipe.
Highly recommended!