Clarification
OK, let me clarify...
Machine specs are as stated above plus dual 160GB HDDs. Dual boot machine: XP on both drives (primary is a stock Dell load, secondary is a majorly modified version of XP), both act the same way with the secondary drive being slightly quicker. Primary drive is for "business use". Secondary is for, well let's say, adult use? I also use an external 640GB HDD for bulk storage so neither of the OS drives have more than 50% usage
My most often used apps are, in order of frequency:
Browser: Firefox 3.5.8 (more often than not I have at least 2-3 browsers open each with several tabs going), takes 2-3 minutes to load on fresh boot seems to stay slow, flash apps are horrible even with high speed connection.
Email: Thunderbird, can take a minute or so to load on fresh boot and then is OK.
Email: MS Outlook, loads quickly on fresh boot.
QuickBooks Pro 2008, takes FOREVER to load, performance fine once running.
Dreamweaver CS4, loads "quick enough", but performance can be lacking with multiple apps open.
Photoshop & Illustrator CS4 take a little bit to load and then run quite slow depending on what I am doing. Horribly slow with multiple apps up and running (Multiple browser tabs, email x2, Pandora in separate browser, etc).
Apps that run at boot time (both boot partitions):
Trend Micro AV
CyberPower UPS utility
Brother Printer utility (takes forever to load)
SnappyFax fax utility (takes even longer to load)
If/when I upgrade to a MAC I'd like it to be a performance upgrade, as well as a usability/security upgrade. I know "once you go MAC you'll never go back" so I expect future upgrades, but I also can't afford to drop $600-800 now, and then another $200-300 to get it workable.
So, given what I have outlined, what would be the minimum specs you would shoot for. And I mean minimum specs not a dream machine... I can create a dream machine, I need a MAC "for now" and when I can afford it I'll buy another bigger, better, badder version.
Lastly I realize this is a subjective question/post, but imagine your a relatively low income family with a newborn.