If by cheap you mean using the portal gun to move a spawner unless you changed the configs I suggest you look at the updated recipe for the portal gun before you call it cheap. if you mean turrets off any sort of normal style mob gen build when I would also suggest just using a melee turtle less noise and you only need one.
Like I have here.
base Upgrades by Saice, on Flickr
I meant using the sentinel turret yes. unless that recipe has been changed too? havent made on in a while.
With soulshards you dont want to move the spawner anymore. you want to collect it's essence to upgrade you shard instead. you can get more productive spawners that way.