Looking to upgrade again, need assistance.

[KubeDawg]

So I'm bout to start upgrading my system here in the next few weeks, and I was wondering what I should do.

Here are my current specs, I know, they're terribad:

AMD Athlon 64 3800+ (not X2)
ASUS A8N Ultra nForce4 Mobo (up to 4 GB RAM w/ PCI-e 16x slot)
nVidia GeForce 8600 GT w/512 MB GDDR3 RAM
2GB(2xGB) OCZ Platinum 184-Pin DDR SDRAM (PC 3200)
Antec earthwatts 500W ATX12V v2.0 SLI Certified CrossFire Ready PSU
500GB Seagate Barracuda 7200 RPM SATA 3.0Gb HDD
ZALMAN 9500A 92mm 2 Ball CPU Cooler

What I'm wondering is, I've recently upgraded my GFX card, added the cooler, and bought 2 GB of new ram. Is it worth it to upgrade my Motherboard/CPU at this point, if I want to take it to the so-called 'next level' to be able to support more high end online gaming? The reason I ask is because I'd likemy PC to be able to handle more loads, such as using Adobe Premier, and recording videos such as in FF, at a much faster rate that won't bogg down my system.

I bought my motherboard a while ago, thinking if I ever needed to upgrade, I'd be fit, because it supports X2 and FX series CPU's for the AMD line. Well, with the new AM2 motherboards out, I'm hearing mostly great things. I'd also likely have to upgrade my RAM...again...

I basically want to be able to purchase something that will be compatible with my current HW(aside from mobo/CPU/maybe ram) that will be able to allow me for future individual upgrades so won't have to purchase 3 types of HW at once.

Which is better now, Intel, or AMD? Will my current gfx card work better on an intel board or an amd board? And finally, is there any support for my current system ram if I were to upgrade my mobo/cpu to some of the newer types?

This is somewhat what I've considered as far as mobos are concerned:
http://www.newegg.com/Product/Produc...82E16813130136
or
http://www.newegg.com/Product/Produc...82E16813188026

For CPU's, I've not really researched enough to know what'd best fit either of those mobos.