Depends on your needs. As WS mentionned, Athlon is better bang-for-buck, but P4 has all that megahertz yumminess.
But let's understand how it works tho. The Athlon has a lower clock speed, but the K7 microarchitecture is slightly more advanced than Intel's P6. That basically means that your 2.08 Ghz Athlon goes nearly as fast as a 2.8 Ghz P4.
Personally, I'm an AMD certified reseller. I do not own a shop, and with time I lost my contacts, but I can easily say that Athlon is the way to go for most home systems. If you want raw power, then P4 is where your heart should be.
The problem with the P4 though is the incredible amount of "CPU bubbles", or unused cycles, in the processor. That basically means that you get many of those megahertz that are not being used, thanks to a design flaw.
But since then, this flaw has been addressed, and from it spawned the Hyper Threading tehnology. Because that's basically how they fixed the problem.
So, if you want a P4, get one with HT otherwise, you'll end up with a slower system than the one advertised (salesmen will NEVER tell you this tho... I would know... I work at Staples as a computer salesman), thanks to the high-ranking folks at Intel.
Now, if you are a special case, such as me, it really depends on your needs. If you do mostly real-time stuff, such as games, then again, P4 is the way to go since it's got raw power.
But if you need that computer for work and calculations, such as Photoshop or 3D animation, then Athlon is the way to go, unless you get a multiple-CPU system.
The only reason why I didn't go Athlon in my dual system is because they run hot. One is already bad enough for most towers, two is overkill. Add a good video card in that, and you're in for a personal heater for your room.
That's why I favored the P4 XEON over the Athlon MP for my workstation. Simply for reliability issues.
And as far as video card goes, go with ATi. NVidia has been found guilty of uneffective driver optimizations that only boost the numbers in benchmarking and increasing framerate in games by reducing visual quality. ATi has great performance for the price. Personally, as a great bargain,I suggest the 9600 PRO. That's what I got, and at 229$CAN, it's quite the deal for the performance it gives, seriously...
And it's nearly on par with NVidia's top in many cases as well. ^^
In any case, it's really a matter of judging your needs and buy accordingly.