Honestly unless I never used content aware in PS CS6 or adjustment brushes in LR 5.x I wouldn't be happy editing on any machine, Mac or PC, that couldn't clock over 3.5GHz. Just too laggy otherwise. 8GB Ram is fine, 4 is too little, 16 only gives a tiny improvement and there is no real advantage going from 16 to 32 for 99+% of users. Also, an SSD for your boot drive really improves performance.
How much machine you need
really depends on your expectations. For example:
- My core i5 Surface Pro2 (1.9 GHz base and 2.9 GHz turbo) with 8GB RAM or our loaded up Macbook Air are a bit underpowered to get great performance from LR5 or CS6, but are certainly ok for light editing. Brushes and content aware healing are noticeably laggy though ... but if you don't need them much you'll probably be happy with those kinds of spec'd machines.
- To get near perfect/zero lag performance from LR 5.x and PS CS6 I upgraded from a very decent, slightly overclocked i7 930 desktop machine with SSD boot drive and 12GB RAM (more powerful than the two laptops mentioned above), which still had laggy brushes and very slow content aware healing in PS (just not nearly as bad), to a slightly overclocked i7 4770K desktop machine (4.2GHz) with SSD for boot drive and 16GB RAM (I later upgraded to 32, with zero additional performance boost).
It's unfortunate, but LR5.x and PS CS6 are total resource hogs compared to LR4.x and CS5. At least LR 5.7 seems to be better than 5.0.
So ... you can go from an elegant little laptop that's easy to carry around, with a lighter weight CPU that gives great battery life, but would be pretty frustrating lag wise for anyone that uses some of the resource hungry tools, to either a very expensive lappy like the highest spec'd Macbook Pro or Lenovo (really expensive) or a monster tower (also can be expensive) that can crunch through any task at blazing speed.
Once you get your new system setup follow Adobe's advice to optimize performance:
http://helpx.adobe.com/lightroom/kb/optimize-performance-lightroom.html . If you get an SSD for your boot drive move your LR backups, catalog files and previews to it, which also speeds things up a bit. You just have to delete some of the backups every once in a while to prevent filling the drive.
I really apologise if the above creates more confusion and I'm not suggesting that you throw a bunch of money around and buy some monster system. It's just good to know that the lower spec'd machines are a compromise, but if it's in areas you could care less about then it certainly could be the best choice for lots of reasons (budget, portability, battery life, etc.).