Depends on lots of things I'm afraid
If you are going for a gaming machine then it would come down to the graphics abilities of each of the cards (processors are pretty similar performance wise).
As to RAM you'll find that most Athlon boards these days will not support SDRAM so you are looking at another expense there.
Basic system I just put together (excluding hard drive and CD/DVD drives):-
£35.00 350W power supply and case
£70.00 Athlon XP2500 Barton Core (runs at 333 and is very overclockable) + FAN
£30.00 ASROCK AS78XE motherboard (as this has 400 FSB potential, new version has serial ATA too for £15 more)
£42.90 512M of PC3200 DDR - bought from PC World who have a sale on of the 256 sticks at the moment)
That gives me enough power to play most of the recent games and is upgradeable. As I have recently bought a few other toys (a 3.0G P4 system and a 2.8G P4 system) I didn't put too much value in a decent graphics card.
£29.00 Geforce MX440 with 8x AGP which offers similar performance to the N-Force board you looked at.
Other ones I considered:
£120 Radeon 9600pro
£50 Radeon 9200 or Geforce 5x00
What it comes down to is the boards that have graphics capabilty built in usually should be treated as a useful extra but not as a replacement for a decent graphics card. For high speed gaming an extra graphics card is always needed.
Oh and