I've used well over 100 enhancers so far, and so far, my results say it's a complete waste of time to do it to low end items. The "good" enhancers (armor enhancers, weapon economy, mining finder skill) give about 10% on the item. As you can imagine, this only makes a difference when the original stats are substantial to begin with. The armor protection ehancer, for example, gives about 10% additional protection. On a ghost, that is a measly 1.9 additional protection impact, and .1 on acid. However, on my apis, having two weapon economy enhancers added about 50% to the life of the gun.
The "bad" enhancers (mining finder range) give 1%. It will take 10 of them to achieve the same result as 1 "good" enhancer.
So, back to your question: should you tier up an opalo? Here are the opalo's basic stats:
8 damage
55 range
.02 pec decay per shot
Adding 1-10% on any of these would be a complete waste of time. You would be paying 10 ped per additional .8 damage, 5m, or .0002 decay saved.
Opalo SGA, on the other hand, has a lot of promise if you keep increasing the range, but even then, it would only be useful as a tagging weapon, and soon the marber bravo will cost the same as opalo sga.