you can demo both if you haven't already.. there is a good guide on their site regarding mastering thats often mentioned here.
I wouldn't say alloy is a lite version.. they might appear that way but how you approach one / many tracks is different. I don't have alloy as I have other plugins also (I have t-tracks singles), as tempted as I would be to get it, I haven't.
quad core is decent enough , but it depends what your running it with / your track count.
lots of companies around , most will offer demos / trials . I've been looking at stuff by melda of late..
www.meldaproduction.com and a few more companies.
but I liked ozone 3, upgraded to 4