The best PCI-E mobo for Amd i can suggest for now would definetly be the ASUS A8N SLI....It can easily support ur 3000+ Athlon 64 proccy Plus it has two PCI-E SLots (SLI Support here boss 8) ) but SIGh!!! no Onboard
graphics support so have to get an geforce 6600 gt card for it
and now the sad part its beyond ur budget (round abt 10k to 15k) but this is the best PCI-E mobo for AMD proccy right now
besides this its quite tough to find PCI-e Supporting mobos for AMD processors
also there is a non-SLI version of A8N with just one PCI-E Slot but no idea what that costs.....so hang on till someone answers and gets hold of some other mobo at ur budget....good luck pal