You'd get better bang for the buck by going with the Athlon, but don't get the 2700+. Get a cheaper cpu. You can whack a few hundred off the price by dropping a hundred mhz or so, and you'd save almost enough money to go for an ATI 9700 or put at least 512 meg DDR on the mobo.
Seriously, an athlon 2100+ is like $87 and a 2400+ is $178 on pricewatch. You'd save at least $100 right there. at the cost of around 100 actual cpu mhz.
If you go for intel, get an 845 board with DDR and buy the fastest cpu you can get because they enabled hyperthreading on their top of the line cpus, and that is good for a nice jump in performance. Oh yea, get a mobo that supports hyperthreading as well. Don't know if the abit one does.
There is also supposed to be an AMD price cut soon, up to 40% price decreases across the board. You might look into when that will happen before buying, and definately check into the new intel hyperthreading support on the cpu and mobo.
And rambus is dead, don't get that stuff.