both PCI and AGP Slots are on the motherboard. You only have one AGP Slot though and generally it's brown and is completely offset from the PCI Slots....
What kind of Intel processor do you have now meaning speedwise? If you get a board like the NF7-S v2 from ABit and a 35w 2400+ XP-M or even the 2600+ XP-M you'll get the barton core with 512k L2 Cache just like that 3200+ XP, the difference is the XP-M's are for 'mobile' hence the M, but they are all socket A, these chips are INSANELY easily overclockable, I got mine running at 2.6GHz at the moment...
There's always debates but generally the rule of thumb is:
AMD = Gaming
Intel = Application use
AMD has shorter pipelines and can do more per instruction clock, whereas Intel has fatter longer pipelines allowing those higher clockspeed, but they don't do as much per clock cycle so thats why they can have a 3GHz chip and AMD only have 2.2 and still be able to keep up...My current OC'd processor will out do a 3.6GHz Intel on some benchmarks, but of course every system varies.
I say if you've been with Intel atleast give AMD a shot