To answer your first question, yes, buy Mach2 - but check out the demo first to be safe!
Just before christmas I spent many days getting EMC up and running, but was never pleased with it. For starters it is difficult to setup, editing the ini file then having to restart EMC every time you need to adjust the settings. This is after/if you manage to install it in the first place of course. The biggest problem I had with it is the 1 second delay between pushing the hotkey to jog the machine, and machine jogging, then releasing the hot-key, the machine continued to jog for a second or so. Maybe it was my system, maybe it was me, but Mach2 was so easy to use compared to EMC, that is was worth every penny for this feature alone! Jeff Davis gave this product a great review in the reviews section of this site, that you may want to check out.