Importance of FSB, limitations of this system

I am planning on upgrading my current PC in the hopes that it will be a viable gaming platform in the interim period while the new technologies settle a bit. I Currently have a 2.0 Willamette core Pentium 4 with a 400mhz frontside bus on a 850 intel chipset.
As you may know this chipset has a 4x AGP, which is not a very good compliment to my 9800 Radeon Pro.
I plan on upgrading the processor to a 2.6 ghz pentium 4.
I would like to know if this is a viable upgrade, the system has 768mb or RDRAM 800.
How limiting is the fronside bus and agp to this system?
I play 3D games, most notably farcry and the new warhammer 40k dawn of war beta.
Will this upgrade provide a benefit, or at this point am i still limited by the video card becuse of the agp bus?
Thanks

Pentium 4 2.0 Ghz
768 mb RDRAM 800
100gig ide harddrive
intel 850 chipset
ati radeo 9800
soundblaster live pro

Ok. So your argument is that the limitations of the bus speeds would invalidate any upgrades of the components?

In your opinion would my system by limited by the video or the cpu.

the upgrade to the 2.6 is what im debating on, the money really isnt an issue since i have a bit of desposable income other than the money save for a new system.

The new processor will yield no real appreciable benefits?

The 4X of your Agp slot is not the bottleneck. Your graphics card would only use all of that, if you could run at max everything.
2.0 gigs is more than enough speed for any game made today. Your problem is memory related. While Rdram is the best way to use the 100mhz fsb, it is still the bottleneck for any of the P4 chips. That is why the P4c is so much better than a P4b, at the same speed. Your best option, if you want better perf now, while waiting for a major upgrade, would be to get an xp-m chip, an nforce board, and some pc3200 DDR. If you clock the xp-m chip to 200 fsb, with a multiplier of 11 or 11.5, you should be OK until the present problems with hardware get ironed out.