Hmm, well the TI4600 is definatly an improvement, but it's not going to be leaps and bounds above the GF3 (maybe 50% faster or so, which certainly isn't bad but I'm not sure if it's worth getting a new card over), and doesn't support any additional features. It's definatly a great card, but I think it might be a good idea to skip every other videocard generation (i.e. GF3 to GFFX/9x00, GF4 to R4x0/GFFX2, etc). I just think you'd be better off saving that $100 and waiting for an FX5900 or even a 9700 to come down in price a bit, THEN you'd definatly notice the difference between the cards (since the FX and 9x00 support better/faster AA modes and have DX9 support). But it's you're call, if you think that the $100 is worth it for the performance increase (or if you're just impatient
), go for it.
Also 512 megs of ram is plenty for most modern games. Only a few MMORPGs really use more, and so far I haven't seen a game that's even remotely unplayable at 512 megs of ram.
Anyway, nice to hear your comp is getting a much-needed upgrade. Even with a GF3, it'll be great for playing almost any game at 800x600 resolution with good framerates, some even a bit higher (I play Natural Selection at 1024x768 with 2xaa/lvl8aniso).