i have had a 930hs, 930spx, and a 930 jm pro (on the way). they are simply great. I did the same thing you plan on doing and got a 28" ported barrel for my spx and took it trap shooting. it was so easy it is boring. it cycled everything i ever fed it and the only problem i ran into was when i tried to see how long i could cycle cheap birdshot before i needed to clean it. fwiw, it was just over 500 rounds. it would still cycle heavy loads. it is very soft shooting and has the ability to ghost load so total capacity is 9 on the spx. one really nice feature is you can dump the mag tube by lifting the loading gate, holding the bolt back, and pressing the bolt release.
as for my only dislike, it was the loading gate. it i wasnt cateful, it would catch my thumb. also, if you dont push the shell all the way it, it would pop out into the carrier.
i ended up selling the spx and hs version to get the 930jm pro and akdal 1919. one thing i would recommend is that if you don't really need the ghost ring sights, get the 18"/28" combo gun and nordic mag tube. the total will be less than a 930spx and you will have both barrels and the capacity. the long barrels from mossberg are ~$150 so the sxp plus long barrel will be well over $700.