Graphics. 6450 = SUCK. Intel 4-series = SUCK. GTS250 isn't a high-end card but it's roughly equivalent to a 9800 or a Radeon 4850. Newer primary model number means only that you have the newer tech like DX11 support. Lower secondary model number means it's usually underclocked, has reduced shader/stream processor capabilities.

Primary model vs Secondary model is like so:
High end: GT 470, GT 260, GT 270
Low end: GT 430, GT 240
High end: 6870, 4870
Low end: 6450, 4830

I'd point you to a comparison chart that shows you how they measure up but those three cards are all now considered entry level/value cards. Not much you're gonna be able to do without upgrading.