I play my sentinels armoured and usually stock. 3 strenght 6 shot's is good against most infantry, light vehicles and the occasional medium armour vehicle (av12, side armour, that kind of stuff), especially in pairs of 3 (9 s6 shots). Taking autocannons makes them only less cheap and loses you an extra shot, which I wouldn't find it worth trading for that extra 1 strength. Onother option would perhaps be taking the plasma's on armoured sentinels, giving them camo and then sticking them behind some solid cover or another tank. I'dd say just have a look at what you think is fun and what you don't have already in your army. Sentinels can basicly be your more mobile heavy weapon squads.
If you're planning on taking many or want orders on them consider the emperors talon recon company. Not only gives it armoured sentinels the possibility to outflanks as well, but you get one commander that can issue from a small selection of orders which aren't bad. It's a fun formation to use that isn't too expensive if you keep your sentinels cheap
Edit: I just saw the date of the post and I'm pretty sure you build that kit a long time ago ^^ but perhaps someone else might find this usefull.