Intel has the faster quad's, but they cost more then the AMD Quad's. I have a Phenon 9600 & like it. It's not the fastest, but I build a whole machine (minus OS) for ~$1300 with that CPU & it's pretty snappy.

Get the next revision though: the 9550 or 9650. They fix some bugs in the original run of Phenom's.

baysidebas, I was thinking along the same lines.

I wonder what kind of hard drive setup is feeding the data to the CPU. The problem could be either CPU or HD related. I would think an AMD 4800+ could handle a few regular DV clips with ease. A RAID 0 with 2+ drives makes a big difference in how many video streams you can play in real time. You could also put separate video clips on multiple drives, but that's always a pain when trying to keep up with what files are where.

When I run uncompressed video I can not get a decent frame rate even on a single clip. But with DV I can do 2-3 time lines (without transitions) pretty smoothly. That means I'm dealing with a HD speed issue on the uncompressed. But with the DV clips, when I add a transition or heavy processing effects, it will usually bog down. That, of course, means it's a CPU issue since I didn't change the bandwidth needs.

If the footage is Mpeg2 or Mpeg4 then those data rates are generally equal or smaller than DV but for my system are much harder to play back. In those situations it has to be the CPU decompression needs that are bogging thigns down.

Now if you determine that it is definitely a CPU (decompression or transition calculation) issue, then supposedly Vegas can make use of more cores for each clip on the time line. As to whether a super fast dual core is just as good as a slow quad core, it's hard to say. You might could check Toms Hardware to see different CPU scores on tests that make use of multiple cores like Cinema 4D and other ray tracing tests.

If you still plan to upgrade the CPU, another issue to consider is the speed of the RAM. I've seen a few AMD 64 motherboards using the older DDR 400 ram instead of DDR2 800. If that's the case then a faster CPU alone might not offer a significant improvement. And along those lines, if I were building a high def computer today, I would splurge for the Intel Xeon systems that can use 1333 ram and then a 64bit OS that can make use of 8GB+.

By the way, I can't wait to see how Vegas 64bit runs a bunch of HD clips.