I would not get Altiverb 6 for Win. I purchased over a year ago, mainly for the cool, cheap sounding spring reverb tanks. Over a year later, they have yet to release Altiverb 7 for Windows, which will be (if it ever arrives) the x64 version. The Altiverb 7 for Mac has been out for close to a year now, with the promise of 7 for Win "soon". In the meantime, all their new reverb samples for over a year now, only work with Altiverb 7. That means no new spaces for Windows users for over a year.
When I purchased, I really thought they were a company well on top of their game. I've have a different opinion of them now. I wouldn't touch Altiverb until v7 x64 is out. Even then, I'd think about waiting until all the bugs are out. They seem to have continuing bugs with v7 for Mac going on for the year it's been out.
If you want some killer reverb... get Acustica Audio's Nebula 3 Pro and VNXT reverb sets. Way ahead of Altiverb in sound quality. And for a great sounding algorithmic reverb... 2cAudio's B2 reverb would be hard to beat. You'd be set for about anything reverb wise. All totaled, about the same price Altiverb 6 for Win would cost you alone, with much better results.
In fact, if you really think you want Altiverb 6 for Win and wanna wait for v7, I'll sell you mine for at least half price of what it would cost you new, and make sure you get the proper license transfer thrown in (if they allow resale... I haven't checked). Let me know if you're interested.