http://thesims2.ea.com/help/detail.php?help_id=21
The TNT is a non T&L (Transform & Lighting) card, so using Software T&L support would demand more from the CPU.
The Geforce 2 (even the lowly 2MX version) has T&L - and I wouldn't say AVOID the Geforce 4MX (I have one), but be aware that the 4MX is basically equivalent to a full Geforce 2 - since I paid only 10 UK pounds for my 4MX, I'm quite happy with the cheap upgrade for an older PC - when I need DX8 or DX9 hardware, I'll have to upgrade again, but by then I'll be looking to scrap this old wreck.