Also, if you already have a fairly reliable windows machine keep it for all the third part apps and utilities and use the Mac for the other stuff. Networked systems are great ans since the newer Mac OS are able to work with long file names now and most of the apps work across platforms you should be in heaven with the best of both worlds.

I went from an old Mac 8600 030 system running Poser 4 and 4 megs of RAM to a new souped up MacBook Pro with 8 gigs of RAM an i7 quad processor with a dual graphics card configuration.

God what a freaking difference.

I have been using  Macs for over 20 years while also using Windows machines  in the design/Digital Retouch and pre-press industry and can tell you I know NO ONE who has taken the step-up to Macs who went back to Windows. With the dual graphics card configuration, built-into  all Macs since the Mac IIci, you can work with a 13 inch MacBook Pro fully rigged and maxed out and plug into a large screen monitor and you be in heaven. The best of both worlds working on a large screen and still having portability when you need it.