Yeah, upgrade to either the freeist or the cheapest modeller when you want to expand?
Bad examples of upgrades mate, those are basic packages designed to teach 3D modelling, not expand it.
Expanding would involve buying a powerful modelling package, one that can render while still being reasonable for low poly work.
To really expand your horizons, grab Rhino3D, go on, have NURBS do your bidding instead of splitting polys and box modelling everytime - not ideal for character modelling, but damn it can knock out mechanical models quickly.

Aegrescit medendo