doormatderek :
bologna, go for a faster dual over a slower quad any day. They are MUCH cheaper/faster and you can upgrade later when AMD gets out decent quads. (45nm)
You're a month behind. AMD already has decent quads out:
http://www.anandtech.com/mb/showdoc.aspx?i=3506
The Phenom II's are 45nm. The Phenom II 920 @ 2.8 and 940 @ 3.0 are AM2+ and DDR2, but new AM3/AM2+ that work with both DDR3 and DDR2 1066 are arriving next Monday. The 3.0 gigahertz version isn't arriving until April though.
There will be several triple and quad cores within a week. What we need to ask the OP is what motherboard does he have (with his CPU, it sounds like an OEM system and not a custom shop or homebuild). Will his motherboard support a Phenom II? Is there a bios update for it? If it's an OEM system, then I'd say not.
OP, you can avoid CPU limitations by gaming at a higher resolution. When the GPU pushes more pixels than the CPU can handle, the GPU slows down. That's the traditional bottleneck. Since a GPU doesn't push as many pixels at higher resolutions, that allows the CPU to be more evenly matched and you get the full benefit of both.
I wouldn't recommend anything higher than a 4830 with a Phenom 9150e. That's more of an HTPC processor than a desktop. It's going into some budget OEM's though.