as far as i know the only difference between the 4200 and 4800 is that the 4800 is AGPx8 optimised. As far as the 4600, its better than the 4200, as far as its existance, i assume it was replaced by the FX, and the 4200 is classed as a semi-entry level card, its cheap and a good performer.
Zik's correct, the 4800 is the AGP8x version of the 4200, the performance increase is probably less than 5%. 4600 is about 15% better than the 4200 if you can still find one.
the FX5800 was the first FX card to be released, but even Nvidia have admitted that they fucked it up (cooling problems, crap performance in older games), and hence released the revised FX5900 recently.
TBH, the raedon cards look more appealing atm, the 9700's are pretty quick and the 9800's are shit hot. Plus they've sorted out the driver problems that used to plague the series.
I've got a GF4 4200 and its a good card for the money, but ive got a feeling it will start to show its age when HL2 and Doom3 are released.
i assume you are refering to your MOBILITY 9000, last time i looked on the ATi webby they said that support for mobility cards was down to the laptop manufacturer, i THINK dell (my Inspiron 8200 be yum) just slightly modified the standard catalysts for use with their mobilitys, maybe its bs, who knows?! but surely Alienware can sort out some decent graphics drivers for their uber hot laptops?
All the hardware sites are hugely pro-ati atm, so they must be doing something right, from reading a few forums it doesnt seem like anyones having problems anymore. The mobile chips might be a different story than the high end cards though.
Nvidia havent always had rock solid drivers, i remember when I first got my GF2 they were flakey as hell. Theyve gone through hundreds of revisions now so they're bound to have ironed all the bugs out. Don't get me wrong, im a huge nvidia fan, but the FX series just looks overpriced for what you get, it's not the huge leap they were promising.
The FX5900 is definitely a superb card, but it's what the 5800 should have been in the first place. When I wrote the above post there were no 5900's for sale in the UK.