what im saying is that the duron will run at 1.3ghz, it just wont be able to use the SSE instruction set it has, which can be of some help to games that are optimized for it (similar to MMX and 3Dnow)
and you are quite correct- geforce 3 is still a very good card, i cant beleive someone would reccoemend a geforce 4MX over it, given that a GF4 MX is nothing more than a slighly faster and redressed GF2, geforce 3 beats the living crap out of all of the geforce 4MX cards and all radeons before the 128mb radeon 8500, which is slighlty better than geforce 3
i wouldnt get a radeon past 8500 series yet, they still have alot of bugs in them that need to be fixed and AGP 8X isnt working correctly on alot of the new radeons
note that i said geforce 3 is better than geforce 4 MX, not the TI, if you get a GF4 TI its better than a geforce 3, and geforce 3 wont be obsolete for at least another 2 years, whereas geforce 4mx will be obsolete in a year
personally im happy with my GF3, and am not going to upgrade till either the radeon 9700 pro bugs are worked out, or GF5 comes and its bugs are worked out.
to get the full potential out of your system and if you want your games to run well, you may as well swap the duron for an athlon XP, its only 10-20 bucks more to get an Athlon XP 1800+, which is 200mhz faster and has more cache then the duron (and also wont be obsolete in 6 months either like the duron will be) and make sure the board has a decent chipset, and that your HD runs 7200rpm for best performance (unless you use raid or scsi)- and i say all of this post from experience, my dad just tried to make a system similar to yours and it sucked, but i got him to take it back and get better componenets which he is haveing a very good time on because the games now run and look kick-*** (but he got a XP1900+)
BTW stay away from the FIC AT Fusion series boards, the onboard radeon graphics WILL NOT work unless you use windows NT, 2000, or XP, becase windows 95, 98, and ME WILL NOT be able to use those boards on board graphics chipset
also it would be best to make sure you have a board with DDR, at least PC2100 (266mhz)as it is now standard, if you can afford it get a 2700(333mhz) capable board with a KT333 chipset (KT400 still has alot of bugs), and i wouldnt go anything under 256mb of ram, 512 if you can afford it, and 768+ if cost isnt a factor