Dunno if you've seen this, but I did a comparison between the newer Heaven models:
There are two things to consider (aside from price) in my humble opinion. First, the higher models---the V and VI---are somewhat more colored than the Heaven IV. The IV is the most linear of the new Heaven series to my ears. Basically, the V and VI will sound a bit warmer and [relatively] more U shaped. The second thing to consider though is that in my opinion the Heaven V gets a definite improvement in spatial rendering over the IV. Basically it sounds more 3D to my ears.
That being said, to me, the difference between the V and VI is much less than the difference between the IV and V. So it's sort of like:
IV ----------> V --> VI
BUT, again, the IV isn't as colored and some folks like that. Also you might not hear that big of an improvement. This kind of thing always varies from person to person, and some of the folks here (BenF for instance) like the Heaven IV a lot more than I do, so you might not find the Heaven V that big of a jump.
Hope that helps!
Edited by MuppetFace - 1/1/14 at 5:35am