Well, the Giggle 3, however nice it is, is a reversible stroller model (more about those here), meaning less spacious in any kind of situation (and yes, the Giigle is even shallower than others). Your next step should, therefore, be to get a non-reversible. world-facing lightweight pushchair for your child, which is the best option for a taller toddler and a logical next stroller that most parents get as their child grows.
My suggestion would be a Baby Jogger City Mini GT2, the ABC Design Avus, the Oyster Zero, or even an Uppababy Minu if you need something smaller... the [[britax-b-motion-4-plus|Britax B-Motion Plus], even if I am not the biggest fan of how it pushes, is also very very roomy.
In any case, this type of under 10 kg, not reversible pushchair will do very nicely for your son. Definitely don't go for something smaller, with a tall 20 months old you'll end up with a child cramped in the seat. And if in doubt, I'd recommend looking at the seatback height, the parents' reviews' (focusing on the roominess), and ideally, going to a store to try out a few to be sure you like the pram as well as the little one likes it (and it is not hell to push with him inside). ^_^