homebuilt system upgrade, 3 options.

hey all.
I currently have a home builmt rig that consists of
asus k8vse deluxe mobo (s754, no agp lock mobo)
Amd 3000+ 2000 mhz
2*512 corsair value ram (non matched)
wd 3200 caviar hd
radeon 9800 pro agp vid card
sb audigy player
Anyway, i'm thinking about doing an upgrade but I could use some advice.

I have 3 routes to go

first option
buy a new agp vid card to stretch the life of the rig a bit longer
this is the cheapest option but agp cards are limited.
i could get a 6600gt for about 180€ or a radeon ax 850 xt for about 500€ the 6600 gt is only a small upgrade if i compare the benchmarks and the 850 xt is overpriced imho, especially since a 7800gt would only cost me 400€ but is not available for AGP  


second option
buy a new mobo, one for s754 and a 7800gt for about 400 for the vid card and 70 for the mobo, this allows me to keep using the cpu and the ram.
MSI K8N NEO3-f, i don't know if this is any good, i've been using alot of msi for friends because i like them, but are not well known with this particular mobo.

for a third option i could do a big upgrade of mobo, mem, cpu and vid card. This would set me back the most but produce the best results.
I'd probably go for a 3500+ or 3800+, msi k8n sli platinum, 2 sticks of 1gb ram and a 7800gt.
but it would cost me definetly the most.

I'm hesitant to replace the cpu and the mem because they do fine still imho
The best option for me seems the second option. With a little luck i can overclock the cpu a good deal, and it's the cheapest acces to pci-X. It also allows me to keep using my cpu and mem, wich are decent enough still for most games.

My needs are built around games, and photoshop.

So any ideas? what would you do if you were me, or what wouldn't you do?
Thanks in advance