1. The biggest bottlenecks for performance comes from:
A. Processor threads
B. HD speed
C. Ram
You ideally want a processor that is hyperthreaded, to offer more threads per core. This will prevent audio drops because the work can be split to different threads. VEP is excellent at this task, which is why even on a single machine using VEP can increase preformance.
I don't know if a phenom is hyperthreaded - I know the i7 is, which with 6 cores would offer 12 threads. Clock speed is still important too, the faster the better. I assume the phenom offers more threads per core, but you would want to double check.
From there, it comes down to HD speed. An SSD will net a lot of perfomance gains. This is how an SSD works - it's practically RAM itself, in terms of access read speeds and can stream a lot more data a lot faster to the processor/ram than a regular HD.
Ram is for loading a large template, of course. I only have 24 gigs myself but that's plenty. I have 3 SSD drives and can load a fairly sizeable template.
2. Honestly, an i5, 12 gig master would probably be fine. More than fine. You want your "beefy" computer to be your slave. I think you would see performance gains by doing a master/slave setup. The CPU/Ram/SDD on the slave is what counts - with a 6 core phenom and a few SSD's + 64 gigs of ram, you're probably set for a massive template if you go with a master/slave set up.
The reason master/slaves work so well is because you're separating your DAW from the audio processing, leaving the master to just worry about the DAW. The audio is piped in from the slave, which processes all the audio and effects, leaving the DAW on the master to simply play it back to you.
When I switched to a master/slave, I saw a big performance boost in my CPU usage. I just have an i7 quad core in my slave and it works wonders. My master is an i7 macbook pro running either digital performer or cubase. Both work flawlessly.
3. You need a gigabit cat-6 or 7 crossover cable to make this work. If it's just a master/slave and you don't need to worry about internet, then you can plug them directly into each other. From there, it's just a matter of going into your network adapter software and changing a few settings. For windows, this is Control Panel/Network and Internet/ Network Connections -> Right click on ethernet properties and then Internet Protocol Version 4(TCP/IPv4) Properties.
A. IP Address on Master: 10.0.0.1, Slave: 10.0.0.2
B: Subnet Mask: 255.255.255.0 on both computers.
This should allow you to connect through VEP. Note that I have to shut off wireless internet on my macbook pro when I first connect. For some reason VEP seems to try and default to that network instead of the LAN setup.
Some other considerations: If you work with dual monitors and you want to use both monitors on your master, you'll need either Microsofts Remote Connection or something like TeamViewer to open and view your slave's desktop.
Hope this is helpful!