Hmmmm, the Mac VS PC debate....
I have been usuing custom built PCs for recording now for about 10 years. I use a company called ADK Pro Audio in Kentucky.
The computers are specked out completely and only for music and specifically with your software and hardware in mind. They sell both Macs and PCs and will work with you to design a computer to your needs and budget.
Now, why would I use a computer builder over building my own custom PC ? Well two things, time and function. They offer a one year warranty, online and phone tech support and the cost was less than $300 more than what I could have built myself. When you take into account the time to build and then the month to tweak and trouble shoot, it was well worth it.
Bottom, line for the price I got a machine which was equal in power to a mac at less money.
I also have a custom built laptop from the same company which is going on 3 years old now that I use for live soft synth work
Now the flipside, I also use a Mac Book pro for all of my professional Graphic design and Photography work, as well as some location recording. It is also my internet and "lifestyle" computer.
I love it! All of my future laptops and home computers will be Macs!
The big question? When it comes time to upgrade my studio computer in a few years will I go Mac...not sure, I would love to, but the prospect of re-buying my software is a consideration.
Also...software. If you love Vegas 2...what does Acid 7 do or not do that you miss as they are virtually the same engine? I am a diehard Nuendo/Cubase user, but I saw you mention Logic, I would soon switch to Pro Tools LE than Logic, just personal taste.
Good luck John!